If your losing sleep give a solicitor a ring to put you at ease,unless UK laws are radically different I can't see him having any comeback but as said,a quick phone call will tell you for sure.
UK law is no different mate, I had the same problem with a car I brought, had it less than 24 hours and the engine decided to blow (oil pump failure). I phoned citizens advice and basically told me I had no real come back unless the guy was linked to motortrade (private sale so no comeback) or he had knew about the problem with the car (which is virtually impossible to prove and just claim ignorance). I then sweet talked the guy I brought it from and he gave me half my money back, atleast I got something back which was better than spunking money down the drain.
If your really worried as said, give a solicitor a call and ask him what kind of act it comes under, then just message the guy back and say, under this act of law you haven't got any come back etc.