I think I'm in trouble with the law?

Evening all... Can someone give me some advice? I played trampoline on this guys car a few weeks ago and dented the roof. The guy who owned it was there but he was drunk and we'd had some extacy, and I did and I was drunk. I was being a moron and I've dented the roof, we pushed it back out but it's now got ripples on it. Thing is, it's actually his dads car and now his dad is after me. He's been looking for me today but I live in London and where it happend is in Wales. Am I going to go to jail if he calls the police? His son didn't actually do much to stop me gettin on the car or tell me off... he was even going to drive the car to the next town off his head on alcohol an drugs but we stopped him, I gave the key to my friends mum. But that's no excuse to jump on the car :( what should I do, he said he's going to ring the police. Shall I deny it? I was gona say we were having hanky panky on the roof... What can they do then?