If you were hoping to pick up an airsoft gun for a few quid then I'm sorry to say I've got bad news, airsofting can be a pretty expensive hobby. Even if you get a G&G Combat Machine, one of the best cheap guns out there, plus a battery, a charger for said battery and a pack or two of BBs its still gonna come out to be around the £200 mark anyway. More if you go with some of the really cool stuff. Even more if you then decide you want attachments and some kit, like a plate carrier or something.
Have you been to any games yet?