There's no stopping... a bird dropping
Don't know if it's already been mentioned, but http://www.stringsdirect.co.uk/ is a beast of a shop, used it a few times now and highly recommend it. They've got a huge list of different strings (cool if you want to explore something other than EB, D'Addario or Rotosound) and offer free shipping if you spend something like over a tenner (couple of packs does it). First class post too, each time I've ordered I've had the strings the NEXT day. Awesome all round service, I wouldn't go anywhere else for strings now (especially as I'm currently hooked on GHS's)!