Been with Plusnet for about 3 months now (previously with Zen and Freeola) and I'm very happy with it.
A few tips though:
Bear in mind, that unlike most other providers, Plusnet count weekend usage towards your cap, so if you're on the cheapest tariff and watch a lot of TV online, you'll go over. They warn you though and it's only a few bob to get the 60GB allowance.
They charge a one-off £5 for a static IP if you want one, rather than BT's £5pcm.
If you're a gamer, you might also want the low-latency upgrade at £5pcm, you see it's all about choice!
I introduced a friend who signed for the same deal I did (6 months free broadband and phone line at £12.99pcm) and I get £1 off my bill per month for the introduction. This offer appears to have no limit, so I believe I could reduce my bill to nothing with enough introductions.
There are short contract options, if I remember correctly, I can buy my way out for @£20 at any time.
You can manage most elements of your account online, including adding the static IP and low-latency option.
So basically, for less than £20pcm, you can have a short contract, phone line rental and diet broadband from a UK company with UK call centres.
So, Plus One, Plusnet