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API Integration & Systems Integration — UK
Your business runs on multiple systems. They should be talking to each other. We make that happen.
API integration is the process of connecting two or more software systems so they exchange data automatically, using APIs (Application Programming Interfaces) as the communication channel. Instead of staff manually exporting from one system and importing into another, an API integration lets your tools share information in real time — without human intervention.
Systems integration is the broader discipline: making your entire technology stack work as a unified whole. APIs are the most common mechanism for achieving it.
The problem we solve
Most UK businesses don’t have one system — they have several. An accounting package, a CRM, a project management tool, an e-commerce platform, maybe a bespoke database that handles something specific to the business. Each one works reasonably well on its own. The problem is that they don’t talk to each other.
The result is a workflow held together by people. Someone re-keys order data from the website into the accounting system. Someone else exports a spreadsheet from the CRM and emails it to the warehouse. A manager manually cross-references three different systems to produce a report that should take seconds to generate.
This isn’t just inefficient — it’s fragile. Manual data handling introduces errors, creates delays, and means that at any given moment, no single system holds the complete, up-to-date picture.
Before integration
- Staff re-keying data between systems
- CSV exports emailed between departments
- Data discrepancies discovered too late
- Reports stitched together from multiple sources
- Customers giving the same information twice
- “Let me check the other system” conversations
After integration
- Data flows automatically between systems
- Single source of truth for each data point
- Errors caught immediately by validation rules
- Real-time dashboards and unified reporting
- Customer information entered once, available everywhere
- Staff freed for work that actually requires a human
API integration solves this by creating automated data bridges between your systems. An order placed on your website appears in your accounting software within seconds. A new lead in your CRM triggers an onboarding email sequence automatically. Stock levels update across all channels the moment a sale is made.
The technology isn’t glamorous — but the operational impact is substantial.
Common integration scenarios
Integration projects come in many shapes, but most fall into a handful of recurring patterns. Here are the scenarios we encounter most often:
E-commerce → Accounting
Orders, payments and refunds from your e-commerce platform flow automatically into Xero, QuickBooks or Sage — with correct VAT treatment, customer details and payment references. No more end-of-day data entry marathons.
CRM → Email Marketing
New contacts and updated segments in your CRM automatically sync to your email platform. When a lead’s status changes, they move to the appropriate email sequence — without someone remembering to do it manually.
Stock & Inventory Sync
A sale on any channel — website, marketplace, in-store POS — immediately updates stock levels everywhere else. Overselling and stockouts become rare rather than routine.
Bespoke System → Everything Else
Your custom business application holds critical data that other tools need. We build APIs that expose that data safely, letting your bespoke system participate in the wider ecosystem instead of sitting in isolation.
Legacy System → Modern Platform
An older system — an Access database, a VB6 application, a classic ASP site — needs to share data with modern cloud tools. We wrap the legacy system with an API layer so it can communicate without requiring the legacy code to change. Often the first step toward full legacy modernisation.
Unified Reporting & Dashboards
Data scattered across multiple systems is pulled into a single reporting layer — giving management real-time visibility across the business without anyone having to manually compile a weekly spreadsheet.
Types of integration
Not every integration is the same. The right approach depends on what you’re connecting, how quickly data needs to move, and how complex the data relationships are.
Third-party API integration
Connecting to existing APIs provided by SaaS platforms like Stripe, Xero, Shopify, HubSpot, or Mailchimp. The API already exists — we build the logic that moves data between it and your other systems.
Often straightforward
1-4 weeks
Custom API development
Building an API from scratch for a system that doesn’t have one — typically a bespoke application or database. This gives external systems a structured, secure way to read and write data.
Moderate complexity
3-8 weeks
Database-level integration
Connecting directly at the database layer when APIs aren’t available or practical. Data is synchronised between SQL databases on a schedule, with conflict resolution and validation built in.
Moderate complexity
2-6 weeks
Multi-system orchestration
Connecting three or more systems into a coordinated workflow — where an event in one system triggers actions across several others. Requires careful design to handle sequencing, error recovery, and data consistency.
Higher complexity
6-12 weeks
Zapier, Make, and no-code platforms — honest assessment
Tools like Zapier and Make (formerly Integromat) are excellent for simple, low-volume integrations. If you need to push new Typeform submissions into a Google Sheet and send a Slack notification, Zapier is the right tool and you don’t need us.
Where these tools hit their limits is with higher data volumes, complex transformation logic, custom business rules, error handling that goes beyond retrying, or connecting to systems that don’t have off-the-shelf connectors. If your integration needs have outgrown no-code tools — or if you’ve tried them and found the results unreliable — that’s typically when a custom-built integration makes more sense.
Platforms and systems we integrate
We’ve built integrations across a broad range of platforms. Below are the ones we work with most frequently, though if your system isn’t listed, that doesn’t mean we can’t integrate it — if it has an API or an accessible database, we can almost certainly connect it.
ACCOUNTING & FINANCE
Xero
QuickBooks
Sage (50, 200, Intacct)
FreeAgent
KashFlow
CRM & SALES
Salesforce
HubSpot
Zoho CRM
Pipedrive
Microsoft Dynamics
E-COMMERCE
Shopify / Shopify Plus
WooCommerce
Magento / Adobe Commerce
BigCommerce
Amazon / eBay marketplaces
PAYMENTS
Stripe
GoCardless
PayPal
WorldPay
Open Banking APIs
EMAIL & MARKETING
Mailchimp
Campaign Monitor
SendGrid / Postmark
ActiveCampaign
Brevo (Sendinblue)
OTHER SYSTEMS
Google Workspace APIs
Microsoft 365 / SharePoint
Twilio (SMS/voice)
Companies House API
Royal Mail / courier APIs
Need to connect systems that aren’t listed here?
This is a snapshot, not a limit. If it has an API or a database, we can almost certainly integrate it. Tell us what you’re working with.
Connecting legacy systems
Some of the most valuable integration projects involve connecting legacy systems — older software that predates the era of APIs and cloud connectivity. These systems often hold years of critical business data, but they sit in isolation because they were never designed to share it.
Common examples include Access databases that can’t talk to anything else, VB6 desktop applications with their own proprietary data format, classic ASP web applications with no API endpoints, and bespoke systems built on older frameworks where the original developer is long gone.
The approach we use most often is to build an API wrapper — a modern REST API layer that sits in front of the legacy system and provides structured, secure access to its data. The legacy code itself doesn’t change. Instead, we create a new layer that reads from (and optionally writes to) the legacy database, exposing the data in a standard format that any modern system can consume.
This achieves two things simultaneously: it solves the immediate integration problem, and it creates a decoupling layer that makes future legacy modernisation far easier — because when you eventually replace the old system, the API contract stays the same, and everything connected to it continues working.
A typical example
A UK distribution company was running their stock management on an Access database and their orders through a Shopify store. Staff were manually checking stock in Access, then updating Shopify availability by hand — twice a day. We built an API that read stock levels from the Access database and pushed updates to Shopify every 15 minutes. Overselling dropped to near zero, staff time recovered was around 10 hours per week, and the Access database continued running exactly as before. Six months later, they commissioned us to migrate the Access data to MySQL and rebuild the front end as a web application — but the Shopify integration didn’t need changing at all, because it was already talking to the API, not directly to Access.
When you need a custom API
If you’re integrating popular SaaS platforms, the APIs already exist — built and maintained by the platform providers. But there are several situations where you need a custom API developed specifically for your business:
Your system doesn’t have an API
This is the most common reason. Bespoke software, legacy applications, and older databases typically don’t expose their data via API. We build one, giving your system the ability to participate in integrations for the first time.
You want to expose your data or services to partners
If your business has data or functionality that external partners need access to — suppliers checking stock levels, clients retrieving reports, or third parties submitting data into your system — a custom API provides controlled, secure access without giving anyone direct database access.
You’re building a product or SaaS platform
If you’re developing a software product, a well-designed API is essential. It powers your own front-end applications (web and mobile), enables third-party integrations, and opens up your platform to a wider ecosystem. We build REST APIs using Laravel and modern .NET — documented, versioned, and secured with authentication and rate limiting.
The existing API doesn’t do what you need
Sometimes a platform has an API, but it doesn’t expose the specific data or functionality your integration requires. In these cases, we may need to build a middleware layer that combines data from the available API with additional data sources, transforming and enriching it before passing it on.
API security is not optional
Every custom API we build includes authentication (typically OAuth 2.0 or API keys), rate limiting to prevent abuse, input validation to protect against injection attacks, and HTTPS encryption in transit. If the API handles personal data, it’s designed with GDPR requirements in mind from the outset — including the ability to locate, export, and delete individual records on request. This isn’t a premium add-on; it’s standard practice.
How an integration project works
1. Scoping conversation
We start by understanding what you need to connect, what data needs to flow between systems, which direction it flows, and what should trigger it. This conversation usually takes 30–60 minutes and gives us enough to produce a proposal. You don’t need to know the technical details — “I need our website orders to appear in Xero automatically” is a perfectly good brief.
2. Technical assessment
We examine the APIs available (or the databases we’ll need to connect to), assess any data transformation required, and identify potential complications — rate limits, missing data fields, authentication requirements, or systems that only support batch rather than real-time data exchange.
3. Integration design
We map out exactly how data will flow: which fields map to which, how conflicts are resolved, what happens when a system is unavailable, and how errors are surfaced. This design document becomes the blueprint and is shared with you before development begins.
4. Development & testing
We build the integration using a staging or sandbox environment where available, so your live systems aren’t affected during development. Each integration point is tested individually and then as a complete workflow, using realistic data scenarios — including edge cases that could cause failures.
5. Go-live & monitoring
The integration goes live with monitoring in place from day one. We track data flow volumes, response times, and error rates. Any issues are caught and addressed before they affect business operations. The first few weeks after go-live typically involve fine-tuning — adjusting sync frequencies, adding edge-case handling, and optimising performance based on real-world usage patterns.
6. Ongoing maintenance
APIs change. Third-party providers deprecate endpoints, update authentication methods, or modify data structures. We offer ongoing maintenance agreements that include monitoring, updates when APIs change, and support when you need to extend the integration to cover new requirements. Alternatively, we provide full documentation and handover if you prefer your own team to manage it going forward.
Ready to connect your systems?
Tell us what you’re trying to connect. We’ll come back with an honest assessment of the approach, timescale, and cost — usually within a couple of working days.
Frequently asked questions
How much does API integration cost in the UK?
A straightforward two-system integration with well-documented APIs typically costs £2,000–£8,000. More complex projects involving multiple systems, custom API development, data transformation, or legacy system connections usually fall in the £8,000–£30,000 range. The main cost factors are: how many systems need connecting, whether the systems have existing APIs, how complex the data mapping is between systems, and whether real-time or scheduled synchronisation is required.
What is the difference between API integration and systems integration?
Systems integration is the broader goal — making your business systems work together as a unified whole. API integration is the most common method used to achieve it. Other integration methods include database-level connections, file-based transfers, and middleware platforms, though APIs have become the standard approach for most modern integrations.
Can you connect my legacy software to modern systems?
Yes — it’s one of our most common project types. We build a custom API layer around the legacy system that exposes its data to modern tools, without modifying the legacy code. This works with Access databases, VB6 applications, classic ASP, older PHP platforms, and other legacy technologies.
Do I need a custom API or can I use an existing one?
Most modern SaaS platforms already have APIs. In those cases, we use the existing API and build the integration logic. You need a custom API when your system doesn’t have one, when you want to expose your own data to partners or applications, or when the existing API doesn’t support the specific operations your integration requires.
How long does an API integration project take?
A simple two-system integration: 1–3 weeks. Multi-system integrations with data transformation: 4–8 weeks. Projects requiring custom APIs for systems that don’t have them, or connecting to legacy platforms: 6–12 weeks. We provide a clear timeline after an initial scoping conversation.
What happens if one of the integrated systems changes or updates?
Well-built integrations are designed for this. We include error handling, monitoring, and API versioning so issues are caught immediately. We offer maintenance agreements that include monitoring and updating integrations when third-party APIs change. Alternatively, we provide full documentation for your team to manage.
Should I use Zapier / Make instead of a custom integration?
For simple, low-volume integrations between popular platforms, Zapier and Make are excellent — and genuinely more cost-effective than hiring a developer. Where they hit limits is with higher data volumes, complex transformation logic, custom business rules, robust error handling, or connecting to systems that don’t have off-the-shelf connectors. If you’ve tried no-code tools and found them unreliable or limiting, that’s typically when a custom-built integration makes more sense.
Will the integration work in real time?
It depends on the systems involved and your requirements. Many integrations use webhooks or event-driven architecture to sync data within seconds. Others use scheduled polling — checking for changes every few minutes. Some legacy systems or APIs with rate limits are better suited to batch synchronisation. We recommend the approach that balances speed, reliability, and cost for your specific situation.
Related services
Legacy modernisation often overlaps with other services we provide. These are the ones most frequently relevant:
Let’s connect your systems
Whether it’s a straightforward Shopify-to-Xero sync, a complex multi-system orchestration, or wrapping a legacy database with a modern API — we’d like to hear about it. No jargon, no pressure, just an honest conversation about what’s possible.