Real numbers. Not ranges that tell you nothing.
2026 UK market pricing
Those are the real numbers for building an AI agent with a UK agency in 2026. The variance is large because "AI agent" means very different things depending on what systems it connects to, how much reasoning it needs to perform, whether it requires a human-facing interface, and what compliance or audit requirements apply.
This guide breaks down what sits behind each tier, how in-house development compares to agency delivery, what to expect in ongoing running costs, what compliance adds in a UK context, and exactly what you need to prepare to get an accurate quote.
Three complexity tiers
Almost every AI agent project falls into one of three tiers. Working out which one you are in gives you a ballpark before you speak to anyone.
1. Single workflow agents
£600 to £4k, delivered in two to four weeks. One clearly defined job against one or two systems: triaging inbound email, pulling fields out of invoices, drafting first-pass replies from a knowledge base, routing leads into a CRM. No bespoke interface, shallow integrations, and success criteria that fit on one page.
2. Connected multi-step agents
£6k to £40k, delivered in six to twelve weeks. The agent spans several systems, carries state across steps, and needs real error handling because a failure halfway through leaves data inconsistent. Most commercial projects land here, and this is the tier where the number of integrations, not the choice of model, decides the final price.
3. Custom platform builds
£40k and upwards, commonly to around £75k, delivered over three to six months. A bespoke interface, several agents coordinating, role-based access, a full audit trail, and usually a regulated environment behind it. At this tier you are commissioning software, not automating a task.
What drives the cost
Integrations are the single biggest driver in most mid-tier projects. Every system you connect, whether a CRM, ERP, ticketing tool, database, or external API, adds engineering time for authentication, data mapping, error handling, and testing. On a six-integration project, expect that line alone to account for £3,000 to £12,000 of the total.
Model and prompt work is rarely the expensive part. Selecting a model, writing the prompts, and tuning them is usually days rather than weeks. The budget goes on everything around the model: getting clean data in, handling the cases where it is wrong, and being able to show afterwards what it did.
Interface work is optional, and it is the first thing to cut when budget is tight. An agent running headless against systems you already own costs materially less than one that needs a review queue, an approval screen, and a permissions model.
Evaluation is the line clients forget most often. An agent that is right most of the time is a liability rather than an asset, so a serious build includes a test set, a measured accuracy threshold, and a defined fallback for when the agent is not confident.
Build in-house or hire an agency
Building in-house makes sense when you need five or more agents over two or more years, want deep domain knowledge embedded permanently in the team, and have the budget and time horizon to justify a full hire.
Agency delivery makes sense when you have one to three defined systems to automate, clear requirements, and a deadline. There is no recruitment overhead and no ramp-up period.
The true cost of in-house is rarely just the salary. Factor in roughly three months to hire, six weeks to ramp, and the risk that the engineer leaves once they have built the first system. For most companies automating one to three workflows, agency delivery is materially cheaper on a total-cost basis.
Ongoing costs after launch
Build cost is one-time. Running cost is not. Budget roughly 15 to 25 per cent of your build cost per year.
That figure covers model and API usage, hosting, monitoring, and the maintenance work that follows when an upstream API changes shape or a prompt stops performing against new data. None of it is optional if the agent is doing real work.
For a mid-tier agent on a £20k build, expect £8,000 to £15,000 per year, which is roughly 40 to 75 per cent of the build cost again over a three-year horizon. Put this in the business case before sign-off rather than discovering it in year two.
What compliance adds in a UK context
The question that decides your compliance bill is simple: does the agent make or materially influence a decision about a person, or does it prepare work that a human then decides on?
If a human decides, the obligations are comparatively light and most commercial automation sits here. Summarising, drafting, retrieving, routing, and prioritising all fall into this category, which is why the majority of projects never reach the higher band.
If the agent decides, you need the safeguards built and documented rather than asserted: a record of how the decision was reached, a route for the person affected to obtain human intervention, and a way for them to contest the outcome. Budget for that as engineering, because that is what it is. In a regulated setting it typically pushes a project into the upper half of the £6k to £40k band rather than adding a separate line.
UK data protection rules on automated decision-making were amended in 2025 and the detail matters to how you scope this. Confirm the current position with your DPO or counsel before committing to a design, rather than relying on any vendor guide including this one.
How to get an accurate quote
Most agencies give vague quotes because clients arrive with vague briefs. The more specific your brief, the tighter and more competitive the pricing you will get back.
Before approaching anyone, be ready to answer five things: which single process you want automated and what currently triggers it, which systems it must read from and write to, what volume it handles per week, who is accountable when the agent gets something wrong, and what a good outcome looks like in a number you already track.
If you cannot answer all five, a paid discovery sprint is the right starting point. Asking for a quote without that information gets you either a range so wide it is useless or a fixed price padded heavily to cover the unknowns.
What Axonari charges
We work on fixed-price scoped projects. No hourly billing, no open-ended retainer for build work, and no change to the number partway through.
The entry point is a £200 paid discovery, which produces a scoped technical brief, an integration map, and a fixed build price. It takes about a week.
That £200 is deducted from your build invoice if you go ahead. If you do not, you keep the brief and are free to take it to any other agency.
Key takeaways
Work out your tier before you ask for a price, because it sets the order of magnitude. Count your integrations, because on mid-tier projects they drive the number more than anything else. Add 15 to 25 per cent of build cost per year for running the thing. And establish early whether a human or the agent makes the final decision, because that single answer moves both the compliance burden and the price.
Get a fixed quote in one week
Book a discovery call. In thirty minutes we will assess your scope and tell you honestly whether a paid discovery makes sense for what you are trying to build.