Frame is at least a 2007 and maybe older up to 2004, but likely 05' onwards due to disc's. Hard to tell from your pic what spec it is. Look on Bike radar, as well as other sites.
From other bikes around I can't see you getting anything over £500 (it looks in good condition) for it, however... It's only worth what someone will pay and it someone thinks its work £KK then great!!