Web and API Development — Web and API Development Bicester by Celsius Software

Systems

Web and API Development That Actually Talks to Your Other Systems

Websites and APIs engineered to work, integrate and last — not just look pretty in a pitch deck.

Most web agencies build you a shopfront and disappear the moment it needs to talk to anything else. We build the shopfront and the plumbing behind it — proper APIs that connect your website to your CRM, your stock system, your payroll, whatever you've got. Twenty-five years in, we've learned that the interesting engineering happens where systems meet, not in the colour of a button. If your current site is a lonely island refusing to integrate with anything, we can fix that, and we'll tell you honestly if it can't be fixed at all.

Features and benefits

What you get

Custom-built, not templated — Web and API Development

Custom-built, not templated

Your business isn't a template, so why is your website? We build to your processes, not a plugin's limitations.

REST and GraphQL APIs — Web and API Development

REST and GraphQL APIs

Clean, documented APIs so your website, apps and internal systems can actually exchange data properly.

Legacy system integration — Web and API Development

Legacy system integration

We've connected new web platforms to systems old enough to vote. Yours probably isn't a challenge.

Secure by design — Web and API Development

Secure by design

Authentication, encryption and GDPR-conscious data handling built in from day one, not bolted on afterwards.

Scalable architecture — Web and API Development

Scalable architecture

Built to handle growth in traffic and data, so you're not rebuilding from scratch the day it starts working.

UK-based support — Web and API Development

UK-based support

When it breaks — and everything breaks eventually — you get a phone number that's answered by a human in Bicester.

Expert insight

Why most web projects fail at the integration stage

The website itself is rarely the problem. The problem is always what happens when that website needs to send an order to your stock system, pull a price from your ERP, or check availability against a diary that lives in entirely different software. That's where cheap builds fall over, because nobody thought about the API layer until it was too late and expensive to fix.

We design the integration first and the pretty bits second, because a beautiful website that can't talk to the rest of your business is just an expensive brochure. Proper API architecture means your web platform can grow with new systems, new partners and new demands without a rebuild every eighteen months.

It also means data only lives in one place, which matters enormously once you're trying to be GDPR-compliant and someone asks you exactly where their personal data sits. We can tell you. Can your current supplier?

How we do it

Six steps to implementation

  1. 01

    Discovery and process mapping

    We map what your business actually does, not what the sales brochure says it does.

  2. 02

    Architecture and integration plan

    We design the API layer and data flow before a single screen is designed.

  3. 03

    Design and build

    Front end and back end built in parallel, tested against real data, not dummy Lorem Ipsum.

  4. 04

    Integration testing

    Every connection to every other system is tested until it stops breaking, then tested again.

  5. 05

    Launch and migration

    We move you live with a proper rollback plan, because hope is not a strategy.

  6. 06

    Support and iteration

    Ongoing UK-based support and enhancements as your business, inevitably, changes its mind.

25+

Years building business software

100+

Systems integrated

UK-wide

Clients supported

Questions

Frequently asked

Do you build APIs for systems that already exist?+

Yes, and honestly it's most of what we do. Legacy systems, ageing databases and bespoke tools built a decade ago are all fair game for a properly documented REST or GraphQL API. We map what the existing system can and can't do, then build an integration layer that lets it talk to your new web platform, CRM, ERP or stock system without a risky rip-and-replace. It's usually far cheaper than starting from scratch, and it means years of historical data don't just get abandoned.

Can you integrate with our existing CRM or ERP?+

Almost always, yes. We've built API integrations into most major UK CRM and ERP platforms, plus plenty of bespoke systems that were never designed to talk to anything else. The approach is the same regardless: understand the data structure, build a secure, documented connection, and test it thoroughly before it goes anywhere near live customer or stock data. If your CRM or ERP genuinely can't be integrated, we'll tell you honestly rather than bill you to find out the hard way.

Is our data GDPR-compliant?+

We design every data flow with GDPR in mind from day one, not as a box-ticking exercise once the build is finished. That means knowing exactly where personal data is stored, who can access it, and how it moves between your website, APIs and any connected CRM, ERP or document management system. If something in your current setup isn't compliant, we'll flag it clearly before launch rather than let it become your problem later. Data protection is engineered in, not bolted on afterwards.

How long does a typical build take?+

It depends entirely on scope — a simple website is weeks, a web platform with multiple API integrations into CRM, ERP or stock systems is naturally longer. We map out the discovery, architecture, build and testing phases upfront so you get a realistic, honest timeline rather than an optimistic one designed to win the pitch. Integration work in particular can reveal surprises in legacy systems, so we build in sensible contingency rather than pretending everything will go perfectly. You'll always know where a project stands and why.

Do you offer ongoing support after launch?+

Yes, ongoing UK-based support is standard rather than an optional extra you get talked into later. Websites, APIs and the systems they connect to all need occasional attention as browsers update, integrations change, and your business grows or adds new requirements. Our Bicester team handles fixes, enhancements and monitoring so problems get caught early rather than discovered by a customer. You get a phone number answered by someone who actually built the system, not a ticket that vanishes into a queue.

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