Full fibre vs leased line, decided properly.
Same fibre technology underneath. Different sharing model, different SLAs, different price. When FTTP with failover is genuinely enough. When a leased line is genuinely needed. Honest engineering economics.
Both run on fibre. The difference is the architecture above it.
FTTP (Fibre To The Premises) business broadband and leased lines both deliver internet connectivity over fibre-optic cable. The actual fibre installed to your building is often identical — modern installations use the same Openreach or CityFibre fibre infrastructure for both products. The difference isn't in the fibre; it's in how that fibre's capacity is allocated and what guarantees come with it.
FTTP business broadband aggregates the capacity from many buildings into a shared backhaul network. Your "500Mbps" connection means you can burst up to 500Mbps when the network has capacity, but you share the aggregation links with neighbouring customers. The pricing model spreads the cost of the shared backhaul across many subscribers, which is why FTTP is significantly cheaper than dedicated services.
Leased lines provide a dedicated point-to-point fibre connection. The bandwidth is yours alone end-to-end — no sharing at any aggregation point. You get the full advertised speed regardless of what anyone else is doing. The pricing reflects that you're paying for dedicated capacity rather than sharing.
Same fibre. Different contracts. Different SLAs. Different prices. Same fundamental physics underneath.
What shared capacity actually means in practice.
Contention is the ratio of customers sharing the same network capacity. Older shared services had high contention (50:1 or worse, meaning 50 customers shared one customer's worth of capacity). Modern FTTP infrastructure has much better contention ratios, but it's still shared.
What this means practically: during off-peak hours, your FTTP runs at or near the headline speed. During peak hours (typically 6pm-10pm for residential-mixed networks; 10am-4pm for business-only segments), the shared capacity is more loaded and your usable speed can dip below headline. For most business use this rarely shows up — typical office workloads don't saturate the connection, so contention is invisible.
When contention does matter: high-utilisation businesses that consistently push the connection — broadcast production, design studios uploading large files all day, multi-site cloud backup operations, businesses with 30+ concurrent video meetings. For these operations the contention can become noticeable, and a leased line's uncontended capacity becomes worth the price difference.
For typical office, retail, hospitality, and SME operations: contention rarely matters in practice. The advertised FTTP speed is what you experience day to day.
The asymmetry that catches businesses out.
FTTP business broadband is typically asymmetric — much faster download than upload. A "500Mbps FTTP" package delivers ~500Mbps download but only ~100-150Mbps upload. A "gigabit FTTP" package: ~900Mbps down, ~110-200Mbps up depending on carrier and product tier.
This matters because business operations are increasingly upload-heavy. Video calls send video upstream. Cloud backups upload constantly. SaaS apps push data continuously. VoIP sends voice up to the cloud platform. The upload speed is often the real bottleneck even when download is far higher than needed.
Leased lines are always symmetric. 100Mbps leased line = 100Mbps in both directions. 1Gbps leased line = 1Gbps both ways. For upload-heavy operations this matches the actual workload pattern.
Symmetric FTTP options exist from some carriers (notably CityFibre's symmetric gigabit, Openreach Single Order Generic Ethernet Access) at premium pricing — typically £80-150/month for symmetric FTTP vs £60-90 for standard asymmetric. Often cheaper than a leased line at similar speeds, with similar functional upload performance, but without the leased line's contractual SLAs.
What "business-grade" actually guarantees.
FTTP business broadband SLAs typically include: business-hours technical support (often 8am-6pm), response time tiers (e.g. 4-hour response for major issues), restoration target windows (e.g. next business day for non-urgent), but few formal uptime guarantees. The SLA is essentially "we'll respond promptly and fix things during business hours" rather than "your service will be up X% of the time, or you get money back".
Leased line SLAs are contractually different. Standard leased line SLAs include: 99.95%+ uptime guarantee, 24/7/365 technical support, 4-8 hour fix windows for outages (sometimes faster for premium tiers), and service credits if the SLA is missed. The credits are real — typically a percentage of monthly fee per missed hour or service degradation period.
What the numbers mean: 99.95% uptime allows ~4.4 hours of downtime per year. 99.99% allows ~53 minutes per year. 99.999% (the "five nines" sometimes quoted for enterprise leased lines) allows ~5 minutes per year. For most businesses 99.95% is plenty. For operations where every minute of downtime has measurable cost, the higher SLAs justify their premium pricing.
36-month cost comparison.
FTTP 500Mbps + 4G/5G failover route (typical UK office):
- FTTP business broadband: ~£60/month × 36 months = £2,160
- 4G/5G failover: ~£25/month × 36 months = £900
- Install: ~£200 one-off
- 3-year total: ~£3,260. Average £90/month all-in.
Leased line 100Mbps symmetric (urban):
- Leased line: ~£300/month × 36 months = £10,800
- Install: ~£1,500 one-off (typical)
- 3-year total: ~£12,300. Average £342/month all-in.
The honest tradeoff: the leased line costs ~£9,000 more over 3 years for: 4 hours of additional uptime guarantee per year, fully symmetric bandwidth, uncontended capacity, and contractually enforceable SLAs with service credits. That's roughly £2,250 per hour of guaranteed additional uptime. For operations where 30 minutes of unplanned downtime costs more than £1,000 in business impact, this maths works. For typical SMEs where downtime is uncomfortable but survivable, FTTP + failover is the rational choice.
The honest decision logic.
Choose FTTP business broadband + failover when:
- Under 50 staff, single site, standard office work
- Downtime tolerance: 4-8 hours uncomfortable but survivable
- Cost pressure on monthly recurring
- FTTP available at your postcode (most UK city/suburban locations)
- Standard hybrid working, cloud apps, video meetings, VoIP
Choose leased line when:
- 50+ staff, mission-critical operations, multi-site networks
- Contractual or regulatory uptime requirements with downtime penalties
- Heavy symmetric upload needs (broadcast, design studios, backup-intensive)
- Production environments where 30 minutes of downtime costs >£1,000
- SD-WAN or MPLS multi-site networking foundation
- Locations where FTTP isn't available (some industrial estates, rural sites)
The case that catches businesses out: "we need a leased line because we have 50 staff." Staff count alone doesn't determine the answer. A 50-person office doing standard office work runs fine on high-tier FTTP. A 15-person broadcast production house genuinely needs a leased line. The right test is operational impact of downtime and the upload-intensity of the workload, not headcount.
It's not always one or the other.
Many UK businesses run hybrid architectures combining FTTP and leased lines across their operation:
Leased line at head office, FTTP at branch offices. Common in retail chains, professional services with branch offices, and franchise operations. Head office where central operations and call centre live gets the leased line; branch sites where work is more standard get FTTP. Connected via SD-WAN or VPN.
FTTP primary, leased line as resilience. Used by smaller businesses where the leased line is the failover rather than primary — particularly where FTTP capacity is good enough for daily operations but the leased line preserves operations during FTTP outages.
Leased line primary, FTTP/4G as resilience. Inverse pattern — leased line for daily operations, secondary connection for failover. Common in operations where uptime is critical but the cost of a fully redundant leased line setup is prohibitive.
Telexico's multi-site SD-WAN deployments typically combine these patterns across locations, with the right connectivity at each site based on its operational profile rather than blanket-applying one product type.
Review my current setup.
Not ready to switch yet? Send us your current contracts, bills, or photos of your existing equipment. We'll review what you have, what you're paying, and where you could simplify, consolidate or improve — without any pressure to buy anything from us.
We benchmark your existing broadband, phones, mobile and IT against current UK market pricing and what your business actually needs.
Real engineer review of your current connectivity, voice setup, WiFi, security and continuity — strengths, gaps, and where you're overpaying or underprotected.
We tell you honestly what's available at your postcode — FTTP, leased line, alt-net carriers — and which makes commercial sense for your operation.
For businesses still on ISDN or aging on-premises PBX — an honest cost-and-feature comparison before the 2027 BT switch-off forces a rushed decision.
No hard sell. No fixed package pressure. If we're not a better fit, we'll tell you straight — and recommend what is.
Frequently asked questions
What's the actual difference between full fibre and a leased line?
Full fibre (FTTP) is a fibre connection from the carrier's network to your building, with the bandwidth shared at aggregation points further upstream with neighbouring businesses. A leased line is a dedicated point-to-point fibre connection — yours alone end-to-end, no sharing. Both run on the same physical fibre technology; the difference is contention (sharing) and the contractual SLAs that come with each. Full fibre is much cheaper because the bandwidth cost is spread across many customers. Leased line costs more because you're paying for dedicated capacity.
Is FTTP good enough or do I really need a leased line?
For most UK SMEs, high-tier FTTP with 4G/5G failover delivers leased-line-equivalent reliability at a fraction of the cost. £60-90/month FTTP + £25/month failover = ~£100/month total. Comparable leased line: £250-500/month. Where leased lines genuinely become the right answer: contractual uptime requirements with measurable downtime cost, symmetric upload needs above what FTTP delivers, multi-site MPLS networks, or where FTTP simply isn't available at your postcode. For typical offices, retail, hospitality with under 50 staff in one site — FTTP plus failover is usually right.
What is contention and why does it matter?
Contention is the ratio of subscribers sharing the same backhaul capacity. FTTP is typically 'up to' speeds (e.g. up to 500Mbps) meaning the headline speed is best-case when the network isn't busy. During peak hours, your actual speed can drop because neighbours are using their share. A leased line is uncontended — you get the full advertised speed regardless of what anyone else is doing. For most business use this rarely matters because FTTP capacity is usually well-provisioned. For high-utilisation businesses (broadcasting, design studios uploading constantly, multi-site backup operations) the contention can become noticeable.
How do the upload speeds compare?
FTTP business broadband is typically asymmetric: 300-500Mbps download but only 100-150Mbps upload on the standard package. Some carriers offer near-symmetric or symmetric FTTP options (CityFibre symmetric gigabit, Openreach Single Order Generic Ethernet Access) at premium prices. Leased lines are always symmetric — same speed up and down. For businesses where upload performance matters (video calls at scale, cloud backup, file uploads, hosting), symmetric is genuinely important. For typical office work where most data flows downward, asymmetric FTTP works fine.
What's the SLA difference?
FTTP business broadband typically has business-grade SLAs with response time tiers (e.g. 4-hour response, next-business-day fix). Leased lines have contractual uptime guarantees (99.95%+ typically) with service credits if SLAs are missed. The leased line SLA is contractually enforceable — if the carrier misses the uptime target, you get money back. FTTP SLAs are more 'best effort with business-hours commitment'. For mission-critical operations the contractual difference matters; for typical office use the practical reliability is similar in most areas.
Can I use FTTP and a leased line together?
Yes — this is a common multi-site or resilience pattern. Primary leased line for production traffic with FTTP as failover. Or leased line at head office, FTTP at branch offices linked via VPN. Or FTTP at small sites and leased line at large sites within the same SD-WAN network. The right architecture depends on operational requirements per location.
What about install timelines?
FTTP business broadband installs are typically 7-14 working days where FTTP is already available at the postcode. Leased line installs are 60-120 working days because the carrier surveys the site, potentially does civil engineering work, and provisions a dedicated circuit. The install timeline difference is one of the practical considerations — if you need connectivity quickly, FTTP is much faster. If you can wait 90 days for the install, leased line opens up.
Tailored around your business.
Send us your current setup. We'll review what you have, what you pay, and where we can simplify, consolidate or improve it — no hard sell, no fixed-package pressure.