What are you looking for? ADSL? ADSL2+? Cable?
Are you a heavy user?
Here are a few to consider for ADSL:
ADSL24
UKFSN
IDNet
Zen
They are all under 3 months contract, the first three are just 1 month with no cancellation fee's.
ADSL24 and UKFSN offer the same package because they are both resellers of Entanet, but they might have different extra's like webspace, emails, etc.
IDnet and Zen are more expensive but all 4 have excellent reviews.