Got pipex too. If you get your own ADSL modem, the contract minimum is one month with solo extreme. There is £50 charge if you quit before 12 months, this is to cover the cost of the administration involved , but this is FAR less then most other ISP's will charge you if you quit before the end of their 12 month contract with you.
Pipex in my opinion sems to have the best ADSL packages at the moment. They seem have the right balence between cost, products and service. This is bourne out I think by the number of statisfied UK PPRuner's using the service.