Well its always best to look at comments from current customers in the forum before choosing your new isp.
There are many now that do not require a 12 month contract and/or give you the modem for free.
One isp is currently doing Broadband for £9.99 a month (+vat) and its not capped, although i have not heard from any customers on it yet.
You could go with a well establised isp thats been around for ages and pay a little more.
Paying slightly more a month than another isp will give you free modem/connection etc. Going for some of the cheaper monthly payment isp's means you have to pay connection fees, pay for hardware or be on a long contract. (always read the T&C's)
Myself i use one of the top10 isps for broadband speed, a Fujitsu FDX 310 modem (Thompson Speedtouch for my laptop).
Oh and if you have not been on broadband before, just make sure you have a firewall and antivirus as a friend got infected within 1 minute of logging is unprotected pc onto broadband for the 1st time.