Mate you did not over step the mark by a long way as what you did was rather restrained mind you if you had found out sooner i think you might of done more.

I properly trashed a so called best mates cossie when i found out he shag my then girlfriend behined my back and tried denying it, after she admitted it to me, so one night i met up with him and let him say his side of the ever changing story, and then grabbed his car keys out the car and lauched them so he would have to get out of the car and face up to me, but after about 20 mins of waiting i decided to have some fun, and lets just say he needed a new bonnet, a complete roof (as it was a little dented) tailgate and a few other bits . he even lied to people how the damage was done as a mate had great pleasure telling his work colleage the truth when one came into his shop.