Also, you can check
Internet Telephone Calling Solutions - DrayTEL :
"Local ('Geographic') Area Code of your choice* You can get your own telephone number with any UK area code you like (e.g. London 020...) for callers to reach you on from anywhere in the world. There are no ongoing rental charges for the number (a call must be received at least once every 60 days to keep the number active/allocated). Only 1 free geographic number is allowed per DrayTEL account after purchasing £10 call credit."