The verdict in three sentences
For a London recruitment agency with 15 consultants, an off-the-shelf ATS such as Bullhorn typically costs between GBP 11,000 and GBP 25,000 a year, and every new seat adds to the bill. A custom ATS requires an investment of roughly GBP 30,000 to GBP 70,000 (2026 ballpark) and 4 to 6 months of delivery, yet it pays back quickly once it cuts shortlisting time by 40 % and tracks fees without spreadsheets. The decision hinges on three numbers: the size of your candidate database, the number of live roles and the share of contingency fees in your revenue.
What a London agency really needs from its ATS
London agencies work in crowded, fast markets: fintech, legal, healthcare, engineering and the public sector. A consultant typically handles 8 to 12 live roles and, according to our audits, spends close to 35 % of their time screening CVs, chasing candidates and re-keying data across tools. A founder who wants to scale is not looking for one more tool but for a system that links CV intake, matching, interviews, client submission and fee invoicing without friction.
Core building blocks for a 15-consultant agency:
- Central candidate database indexing 40,000 profiles, with automatic de-duplication and skills parsing.
- AI matching that ranks profiles against the job spec, past placements and commuting distance.
- Per-role pipeline in a Kanban view, shared with the client through a secure portal.
- Fee tracking: retainers, placement fees, rebate periods and automatic reminders.
- UK GDPR compliance: retention periods, consent, logged right to erasure, and right-to-work checks recorded.
Bullhorn-type SaaS or custom build: the numbers
| Criterion | Off-the-shelf ATS (Bullhorn type) | Custom ATS |
|---|---|---|
| Setup cost | GBP 0 to 5,000 implementation | GBP 30,000 to 70,000 |
| Recurring cost | GBP 60 to 140 per consultant per month | Hosting and maintenance, quoted |
| Annual cost for 15 consultants | GBP 11,000 to 25,000 | Maintenance only after delivery |
| AI matching | Generic, often a paid add-on | Trained on your own placements |
| Fee tracking | Basic or via a separate back office | Native, linked to accounting |
| Data ownership | Held by the vendor | Yours, exportable at any time |
| Time to go live | 3 to 8 weeks | 4 to 6 months |
Over five years, a SaaS ATS at GBP 100 per consultant comes to GBP 90,000 for 15 consultants, before annual price increases of 5 to 8 %. A custom ATS at GBP 55,000 plus maintenance sits in the same range, but the agency owns it and can add consultants without paying per seat.
A detailed budget for a custom ATS
| Module | Share of budget | 2026 ballpark (GBP) |
|---|---|---|
| Candidate database, parsing, full-text search | 20 % | 6,000 to 14,000 |
| AI matching and scoring | 18 % | 5,400 to 12,600 |
| Role pipeline and client portal | 17 % | 5,100 to 11,900 |
| Fees, invoicing, reminders | 15 % | 4,500 to 10,500 |
| Integrations (job boards, LinkedIn, calendar, email) | 15 % | 4,500 to 10,500 |
| UK GDPR, security, audit log | 8 % | 2,400 to 5,600 |
| Testing, training, data migration | 7 % | 2,100 to 4,900 |
A typical schedule runs 4 to 6 months: 3 weeks of discovery with consultants, 8 to 14 weeks of development in two-week sprints, 3 weeks migrating the 40,000 existing profiles and 2 weeks of live testing. Migration is often underestimated: a poorly structured export from Bullhorn or another tool can cost a full week of clean-up on its own.
Mini case study
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Emma runs a 15-consultant recruitment agency in London focused on fintech and legal roles. Each consultant spends 12 hours a week on shortlisting. A 40 % reduction frees 4.8 hours per consultant per week, or 72 hours a week across the team. Over 45 working weeks that is 3,240 hours. If a third of that time goes back into headhunting and the agency makes one extra placement per 100 hours, it gains around 32 placements a year. At an average fee of GBP 8,000, the potential upside is GBP 256,000, against a GBP 55,000 build. Even if you divide that assumption by four, the ATS pays for itself within a year.
FAQ
How much does a custom ATS cost for 15 consultants?
The 2026 ballpark is GBP 30,000 to 70,000 depending on the AI scope and the number of integrations. The final figure depends mostly on database migration and the client portal.
Is AI matching compliant with UK GDPR and the EU AI Act?
Yes, provided the final decision stays human, criteria are explainable and candidates are informed. Recruitment is a high-risk use case under the EU AI Act, which matters if you place candidates in the EU, so plan a decision log and a bias review at least once a year.
Can we keep Bullhorn running during the transition?
Yes, a 2 to 4 week parallel run is recommended. The 40,000 profiles are migrated in two waves to check de-duplication quality before the final switch.
What gains should we expect in year one?
Agencies usually see a 30 to 40 % cut in shortlisting time and first candidate submissions brought down from 10 to 5 working days. Automated fee tracking also shortens payment delays by 15 to 25 days.
Is a custom ATS worth it below 10 consultants?
Rarely. Below 8 to 10 consultants, a SaaS at around GBP 60 per seat is usually cheaper, unless your search method or fee model is highly specific.
Let's scope your project. We will define your priority modules, the migration of your candidate database and a phased delivery schedule with you. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
