My son bought a car at the weekend and in order to get it through the MOT the then owner had a new tyre put on. My son has just phoned me to say that the wheel came off as he was driving along (thank God he wasn't on the motorway)! There is extensive damage to bodywork of his car--where do we stand legally as my son only has 3rd party insurance.
Surely it is the fault of the garage that replaced the worn tyre. Proving that they didn't tighten it up properly afterwards will be difficult though... with hindsight your son should've checked it before driving off...
The RAC have looked at it and photographed the wheel and damage. The spacer for the tyre was put on the wrong way round and hammered into place. Wheel nuts too short so the thread was stripped. I won't bore you with it all, but suddenly they can't remember who changed the tyre.
Luckily my son was only doing 5mph as he was parking at the time, but the wheel flew off and could have hurt someone--the RAC guy said that if he was going faster, the car would have flipped.
I would get the RAC to do a full check on it. There may be other dangerous faults. If there are demand your money back . Even a second hand car has to be fit for purpose.