I believe that ISDN is availible everywhere in the UK. ISDN is a standard that uses two telephone lines to increase your data throughput. As for ADSL, which is the new 'broadband' standard, that's a seperate question. For both, try http://www.bt.com
and look up 'ISDN' and http://www.btopenworld.com/
and look at the 'availibility' screen. Good luck!