Zen and PlusNet differ somewhat in philosophy, but both are clearly very competent providers with attractive products.
Zen's primary focus is on the business market, though they have always catered for home customers wanting a premium product and might well be more active in this market than historically was the case. If you want, you can buy a Zen leased line or a Zen multi-line VoIP solutions.
Zen's philosophy is typically to operate their broadband services in a way where no contention will be noticed at the links into their network and beyond. They have installed their own points of presence in approximately 200 exchanges; where GEA-FTTx handover takes place at an exchange with Zen presence, Zen use their own network for backhaul. In all other areas, Zen use BT Wholesale WBMC. There is no price difference between 'on network' and 'off network' users.
Zen's customer service operation is UK based. In my experience, you get through with minimal delay to someone who is technically adept - there does not seem to be any first line staff who can only trot out standard solutions. You can get a flavour of Zen customer service from the issues I had last week, which turned out to be a BT Wholesale fault in Milton Keynes
With Zen, a static IPv4 address is standard. I believe IPv4 blocks are still available on request if you can provide RIPE justification for them - historically customers could have a /29 free of charge and larger blocks for a one-off fee (I gave extensive technical justification for two non-NAT subnets, for which a /28 is the minimum allocation, so I have a /28). With IPv4 depletion, I suspect the threshold for allocating multiple IPv4 addresses is now rather higher, though if you can justify why NAT is not a complete solution for you, Zen may still be able to help.
Zen have said IPv6 is part of their roadmap, but have said they will not launch it until they have a complete product. For now, I use SixXS via the gblon2 PoP, at the cost of 7ms latency (the RTT from Zen's network in Manchester to LINX) and 20 bytes per packet (for the IPv4 protocol 41 encapsulation). I look forward to native IPv6 from Zen, though am aware that I am in a minority in operating a router/firewall with full IPv6 support (in my case, a rack mount server running pfSense
Zen's minimum contract period for FTTx is 12 months, reflecting the minimum 12 month period of the underlying BT Openreach GEA-FTTx connection.
PlusNet are primarily if not entirely targeting at the residential market. I have never used their services personally, though I have recommended them to several people looking for a quality residential broadband product at a competitive price.
My impression is that PlusNet operate their network somewhat closer to saturation than Zen do, in order to keep their BT Wholesale backhaul costs down, but their use of traffic management typically ensures any contention has minimal impact on the customer experience.
PlusNet use the BT Wholesale network in all areas. Their pricing depends on the Ofcom 'market' classification of the exchange, with Market 1 customers paying a supplement over the listed prices.
PlusNet's customer support is UK based, and seems to go down well with the majority of their users.
With PlusNet, a single static IPv4 address can be obtained for a one-off fee of £5. Routed IPv4 blocks are not possible. PlusNet have not announced any IPv6 plans.
PlusNet's minimum period for FTTx is 18 months.
Ultimately, you must balance up the factors. We rely on our Internet connection for business purposes, and have found it easy over the ten years we have been with Zen to justify the relatively small monthly premium over consumer ISPs.
Of course, any form of Internet connection is fallible and DSL does not carry a service level agreement. We have backups for the occasional outage, primarily mobile broadband contracts on two different mobile networks.
It sounds like both Zen and PlusNet would be a good match to your needs.
If you are seriously considering Zen, make sure you think critically about the speed estimate. If your line is unlikely to manage much more than 40/10 Mbit/s, you can save £3/month by taking Unlimited Fibre 1, which is based on the 40/10 wholesale product rather than the more expensive 80/20 wholesale product. Unfortunately, the £30 activation fee on Unlimited Fibre 1 wipes out this small saving for the first ten months.
Edited by David_W (Fri 04-Oct-13 19:09:44)