In reply to gavinpeach:
Currently using a Veho Muvi K2 NPNG - quite small if you don't use the waterproof case and decent battery life. Cost me about £120 from Argos on eBay - refurb ones from about £75. Comes with all the mounts you need, including self-adhesive*, and you can get a silicone case to protect it from knocks climbing.
* - my only niggle is some of the mounting screws are a bit on the short side.