I've seen a few posings here for people wanting/using geographic numbers to dialup their ISPs, supposedly taking advantage of "free" local/national access through their BT plan.
BE AWARE that BT keeps a database of geographic dialup numbers of ISPs which you should check before you start clocking up hours of calls.
you can check the number here:
http://www.bt.com/Choices/isp_excl.jspBrad.