I've just agreed a new contract too .. 
You should never have to agree to a new contract. This is their way of keeping you locked to them for another term which is mostly 12 or 18 months. What was their reason for asking you to sign up to a new contract?
AOL UK used to have an uncapped service now they ARE capped. Download too much and you'll have slow speeds during the day time. We get about 285Kb/s during the day and up to 500Kb/s during the night/early hours.
Here's some other information which may help...
Don't go with Virgin (aka Telewest Broadband, NTL, Eurobell) as they severely cap their customers. We were with Virgin with a 20MB line and got as fast as 50Kb/s during the day and only twice did we hit max line speed of 2100Kb/s during the night/early hours with about 300Kb/s at other times. We were with them for about 1 month until we terminated their contract for them.
I know a few people with
Be There and they don't care what you download or how much at a far cheaper price than anything I've seen. This is who we'll be moving to when our AO(hel)L contract expires.