The verdict in three sentences
For a 600-employee London company, a custom employee self-service portal costs a 2026 ballpark of 45,000 to 110,000 GBP depending on integrations, delivered in 10 to 14 weeks, while a SaaS HRIS like BambooHR runs roughly 5 to 9 GBP per employee per month. The return comes first from time saved: about 3 days per month per HR administrator no longer typing reference letters or chasing leave forms. Custom wins when your workflows, payroll bureau or union agreements do not fit a standard product; SaaS wins when they do.
What manual HR admin really costs at 600 staff
Even in London, many mid-sized firms still run leave through email chains and spreadsheets, produce employment and salary reference letters by hand for mortgage lenders and landlords, and email payslips as attachments. At 600 staff, that typically means 80 to 120 leave requests a month, 40 to 60 reference letters and 600 payslips, plus a steady flow of bank detail and address changes.
| Monthly HR task | Volume for 600 staff | Time when manual | Time with a portal |
|---|---|---|---|
| Leave requests | 80 to 120 | 15 min each | 2 min approval |
| Employment and salary letters | 40 to 60 | 20 min each | Automatic generation |
| Payslip distribution | 600 | 1 to 2 days of emailing and checks | Published in 1 click |
| Bank and address updates | 20 to 30 | 10 min each | Employee entry, HR approval |
| Leave balance questions | 50 to 80 | 5 min each | Self-service lookup |
| Document filing | Ongoing | Shared drives and folders | Digital file per employee |
A team of 4 HR administrators recovers roughly 3 days each per month, or 12 days in total, redirected to recruitment, onboarding and employee relations.
Custom build vs BambooHR and other SaaS
A self-service portal is not a payroll engine. It sits on top of your payroll provider or bureau and acts as the interface between HR and staff. Here is how the options compare for 600 employees in 2026.
| Option | Scope | 2026 ballpark (GBP) | Lead time |
|---|---|---|---|
| BambooHR or similar SaaS | Standard leave, documents, directory, reports | 36,000 to 65,000 per year | 6 to 10 weeks onboarding |
| Custom essential | Leave approval chain, letters, directory | 45,000 to 60,000 one-off | 10 weeks |
| Custom intermediate | Essential + payslips, digital employee file, notifications | 60,000 to 85,000 one-off | 12 weeks |
| Custom advanced | Intermediate + payroll import, reviews, expenses, HR dashboard | 85,000 to 110,000 one-off | 14 weeks |
| Maintenance and hosting | Fixes, backups, minor changes | Quoted to scope | Ongoing |
Over five years, a SaaS licence at around 50,000 GBP a year reaches 250,000 GBP, while a custom advanced build plus maintenance often lands well below that. The trade-off is that you own the roadmap and the upkeep. Kolonell scopes and quotes custom web applications case by case.
Technical choices that matter in London
UK GDPR and the Data Protection Act 2018 govern employee data, so payslips and personal files need individual access, encryption and an audit trail. Statutory leave in the UK is 5.6 weeks (28 days for a full-time worker, which can include bank holidays), and many firms add contractual days, carry-over rules and part-time pro-rating: the leave engine must model all of these. Single sign-on with Microsoft 365 or Google Workspace avoids yet another password, and a mobile-friendly progressive web app reaches shift workers, field staff and warehouse teams without an app store release.
Integration with the payroll provider (Sage, Xero Payroll, or an outsourced bureau) is the main cost driver: a clean API takes about 1 week, a CSV export with manual mapping 2 to 3 weeks.
Mini case study
Rachel, HR Director of a 600-person logistics company in London, has 4 HR administrators on 38,000 GBP a year, about 46,000 GBP with employer costs. One working day costs about 210 GBP (46,000 divided by 220 days).
Need a professional website?
Kolonell builds websites that attract clients, optimized for the Sénégalese market. Free quote in 2 minutes.
Monthly gain: 3 days times 4 administrators, so 12 days, or 2,520 GBP. Add about 300 GBP a month saved on printing and courier for paper forms. Total: 2,820 GBP per month, around 33,800 GBP per year.
BambooHR-type licence: about 7 GBP per employee per month, so 4,200 GBP per month, 50,400 GBP per year. Custom intermediate portal at 72,000 GBP with maintenance assumed at 1,000 GBP per month: over 5 years, 132,000 GBP versus 252,000 GBP for SaaS. Time savings alone pay back the build in about 26 months, and the 5-year saving versus SaaS is around 120,000 GBP.
FAQ
Does the portal replace our payroll software?
No, it connects to it. Importing payslips and balances automatically adds 1 to 3 weeks depending on whether your provider offers an API or a CSV export.
Can shift workers without a desk use it?
Yes, through a progressive web app on their own phone, under 2 MB, with SSO or one-time codes. A shared kiosk tablet per site costs around 300 to 500 GBP.
How long does rollout take?
About 10 to 14 weeks to build, then 2 to 4 weeks of staged rollout by department. Training 600 people usually takes 30 minutes per group of 20.
Is custom really cheaper than BambooHR?
Only beyond roughly 300 to 400 staff, or when your workflows do not fit a standard product. Under 200 employees, a SaaS at 5 to 9 GBP per head per month is usually the better choice.
Can we start small?
Yes, the essential scope at around 45,000 GBP covers leave and letters, which deliver most of the time savings. Payslips and payroll import can follow in 4 to 6 weeks.
Let's scope your project. Share your headcount, approval chains and payroll provider, and we will define the scope and a 10 to 14 week plan. 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.
