Some guy at work is really doing my head in!!

[CFH]

Wait till he leaves now its dark and wrap a baseball bat round his head

Solid advice. However, I'd do my best to ignore him bro. He's middle-aged and working full-time at a supermarket, life is already kicking his ass for you. I'd wager no one there has any respect for him anyways, so I doubt they take what he says to heart. This is your first job, and you're going to need a reference from it, so beating him to a bloody pulp would probably be detrimental to your future employment, not to mention the negative effects a criminal record would carry. You'd be hurting yourself by doing that, in my experience anyways.

If it gets really bad and it's making you not want to go to work etc., then go to his boss about it (unless they're friends or something). I like the idea of asking him to move you to a dept. where you won't have to deal with the idiot.

Good luck mate.