For a 50-person UK firm, Zen Internet is the easier choice when you want published prices that stay fixed for the whole contract, while BT Business is the stronger pick when a leased line with a 100% availability SLA and a 5-hour target fix time matters most. Both sell leased lines, full fibre, cloud voice and managed networks, so the right answer depends on which of those you are buying and how much price certainty you need.
BT Business vs Zen Internet for leased lines and uptime
A leased line is a private, uncontended fibre connection with the same upload and download speed. For a 50-person office that runs cloud apps, video calls and a hosted phone system, it is often the connection that everything else depends on.
BT's BTnet leased line page lists speeds of up to 10Gbps, a 100% availability SLA, a 5-hour target fix time and 24/7 rapid issue resolution. BT's help pages add that the SLA pays money back if BT misses its commitment, and that it also covers latency and installation. BT does not show a starting price on the page, so expect a quote after a site survey.
Zen's leased line page publishes a starting price of £48 a month excluding VAT, speeds up to 10Gbps, 99.9% uptime as standard and 100% with its resilience option. Zen says a UK-based network operations centre monitors lines 24/7, with Cisco and Fortinet router and firewall options.
The headline percentages are not like for like. BT's 100% figure applies to a single BTnet line, while Zen reaches 100% only with the resilient option. Ask both for the same speed, the same term and the same resilience, then compare the service credit each pays when it misses the target.
Which is better value for small business broadband
If a 50-person office does not need a leased line, business full fibre is the cheaper route. Zen lists Full Fibre 100 at £30 a month, Full Fibre 300 at £34, Full Fibre 500 at £38 and Full Fibre 900 at £46, all excluding VAT on 18-month contracts. Its Contract Price Promise says the monthly price does not rise during the contract, and each tier includes a static IP address and a router with guest Wi-Fi.
Zen business full fibre price by speed tier
Published starting price per month, excluding VAT, on 18-month contracts
View the data
| Category | £ per month, ex VAT |
|---|---|
| Full Fibre 100 | £30.00 |
| Full Fibre 300 | £34.00 |
| Full Fibre 500 | £38.00 |
| Full Fibre 900 | £46.00 |
BT Business Broadband deals are sold on 36-month contracts. BT's pricing terms say broadband-only products rise by £3 a month on 1 April each year, and bundles by £4. BT prices depend on your postcode, so get a quote for your address before you compare.
Upload speed matters more than download speed for a busy office. Zen lists 18Mbps upload on Full Fibre 100 and 100Mbps on Full Fibre 900, so a team that sends large files or runs many video calls should look at the higher tiers or a leased line.
BT Business vs Zen Internet for cloud voice and VoIP
Both firms sell hosted phone systems priced per user. For 50 seats, compare multi-user systems, not single-line products.
Zen CloudComms runs on 36-month terms with a free handset: Solo at £7.99, Essential at £11.49, Professional at £14.49 and Premium at £17.49 per user per month. Zen says CloudComms runs on any business broadband. Zen Digital Voice, at £6.25 a month for 1,000 UK minutes or £12.50 for unlimited UK calls, is sold as a single-line replacement rather than an office phone system.
BT Cloud Voice is sold on a 60-month licence: Basic at £10.52, Connect at £13.74 and Collaborate at £20.09 a month, all excluding VAT. Each licence rises by £1 on 1 April every year. BT also sells Digital Voice for Business from £15 per user, and its online buy buttons for that product are labelled for teams of up to 10 employees.
Cloud voice price per user per month, Zen CloudComms and BT Cloud Voice
Published monthly price per user or licence, excluding VAT, for each tier as listed on 15 November 2026
View the data
| Category | £ per user per month, ex VAT |
|---|---|
| Zen Solo | £7.99 |
| Zen Essential | £11.49 |
| Zen Professional | £14.49 |
| Zen Premium | £17.49 |
| BT Basic | £10.52 |
| BT Connect | £13.74 |
| BT Collaborate | £20.09 |
At 50 seats, Zen CloudComms Essential works out at £574.50 a month and BT Cloud Voice Connect at £687 a month, before VAT, handsets and call bundles. BT's yearly £1 rise adds £50 a month across 50 licences each April. The tiers include different features, so match call recording, hunt groups and Webex access before you compare totals.
Engineer support, aftercare and customer service
Support hours vary by product, so ask for the care schedule of the exact service you are buying. Zen lists technical support from 08:00 to 20:00 Monday to Friday and 09:00 to 17:00 at weekends, with optional care levels for faster fixes on broadband. Its leased lines add 24/7 proactive monitoring.
BT lists 24/7 rapid issue resolution and a 5-hour target fix on BTnet. Its business broadband is a separate product and does not carry the BTnet fix target.
Neither firm publishes figures that let you rank them head to head on business customer service. Ask each for the restoration target, whether the clock pauses out of hours, who sends the engineer, and how you escalate a fault that runs past the target.
Managed networks and SD-WAN for growing firms
Both BT and Zen sell SD-WAN and managed networking. For a single-site 50-person firm, a managed WAN may be more than you need. For a group with several offices, the way the supplier handles faults across sites often matters more than the price of each circuit.
When you tender, give both the same brief: number of sites, primary and backup circuits, who owns the hardware, firewall management, monitoring hours and the restoration target. Ask whether the supplier manages your office Wi-Fi and switches, or only the links between sites.
Switching suppliers before the January 2027 deadline
Openreach says all traditional phone lines go digital on 31 January 2027. It advises checking anything connected to a phone line, such as alarms, CCTV and payment terminals, before you switch. Lines that miss the date may move to its temporary Emergency Voice and Access Continuity service.
If you are thinking about moving from Zen to BT, or the other way, check your exit charges, number porting dates and equipment compatibility first. Neither the BT nor the Zen pages we checked mention paying off an old phone system or terminal lease, so ask for any contribution in writing and get a settlement figure from your current lessor.
Some protections are narrower than buyers expect. Ofcom's rules for providers cover small businesses with up to 10 employees, so a 50-person firm should not assume the same complaint and switching rights apply. Put the porting and cease dates in your contract.
How to choose between BT Business and Zen Internet
Shortlist Zen if you want published broadband and voice prices that do not rise in the contract, shorter terms and a supplier that names its UK-based support. Shortlist BT if your office cannot work without connectivity and you want BTnet's 100% availability SLA and 5-hour target fix, or one supplier for fibre and voice.
For most 50-person firms, the sensible step is to get both quotes for the same leased line speed, the same resilience and the same number of voice seats. Then compare the total over the contract, including yearly rises, rather than the first month's price.
Sources
- BT Business, BTnet leased line, 2026
- BT Business, What does the BTnet Service Level Agreement cover, 2026
- BT Business, Cloud Voice, 2026
- BT Business, Digital Voice for Business, 2026
- BT Business, Broadband and phone deals, 2026
- Zen Internet, Leased lines, 2026
- Zen Internet, Business full fibre broadband, 2026
- Zen Internet, CloudComms, 2026
- Zen Internet, Digital Voice, 2026
- Openreach, Switching off PSTN across the UK, 2026
- Ofcom, A summary of Ofcom's rules for phone and broadband providers, 2026
