Im not twisting that at all, he paid the agreed price less 50 quid which he still owes you, I dont dispute that at all as Ive not spoken to Matt about it to hear any different so Im quite happy to take your word for it, I dont consider you to be a liar over money.

However, when you buy a car and a serious fault comes to light straight away, the seller is obligated to fix it IMHO (and I beleive in the eyes of the law) so I think that Matts request to keep the 50 quid towards rectifying that fault is a fair request and if I was the seller I would happily honour that request and would just be greatful I didnt get the car brought back to me to rectify it myself.