Another option worth considering is a "no contract" pay-as-you-go option where there are no monthly fees at all and you pay simply the local call rate for the time you are connected.

Before I moved to ADSL, I was registered with two ISP's (hey it is free!) - www.zoom.co.uk & www.virgin.net both were great and unless I really hammered the service with overnight downloads never cost me more than £10 / month (worth about 17 hours surf time, off peak)

Downsides are obvious, if you want to use the service regularly during peak hours, you may as well be on contract @ £12 - £15 / month

Off peak local calls, 6pm - 8am weekdays and ALL weekend cost 1p / minute
Peak rate local calls, 8am - 6pm weekdays cost a smidge under 4p / min

Cheers, Sim