Sky. No question about it. If you're looking for unlimited, boy are they unlimited. Unrestricted speeds all day and virtually no limits on usage. It's also very cheap and I've found the support to be helpful.
Stick your number in the Sky broadband availability checker and see what they say.
Edit: I was on Plusnet Unlimited prior to switching to Sky. They switchover was easy as anything and I've seen a massive performance increase (not just basing that on speeds).
Only caution would be the static IP. Sky may do them if you ask, if you need the S. IP for definite, TalkTalk are as good just don't use their phone customer service.
Sky Broadband Unlimited
Edited by Xplosion (Tue 02-Oct-12 13:35:16)