I went to the party in the end. It was a good night, I got back about an hour ago. Things worked out fine, I stayed with my friends and he seemed to wander around aimlessly. There was one time when I was on the dance floor and he came over, but people let me know and I just kept clear of him.

Operation Payback has already begun. My room mate also said that I wouldn't beat him physically, but that I had my strengths in other areas (for example, I'm not repeating my final year of school, I'm not insisting that I hate my ex-girlfriend all day and then professing my undying love for her in moments of drunkeness etc.) so there are plenty of other ways to sort him out. His ex can find out what he says when he's drunk when I see her on Monday. There is already an anonymous tip on where to find him if he doesn't go to his first few lessons of the day. Plus some Polish guy told me that next time, I should go downstairs and wake him up if I wanted to kick his head in.

Thanks for the advice, I guess I just needed to hear the same thing a few more times.