What movie is this, please help?!

ok, its about this dude, i think in real life hes british or somethig!. and he invites this girl who's his friend to his sisters wedding!. he loves her but she falls for this other guy, and then the first dude whos name is buddy gets mad and drunk and jumps of a cliff but i don't think he dies i think that later he dies after getting hit my a car or something while the girl and other guy are having sex!. but its like told as this old ladies memory!.

thanks i know there not a lot to go on!.Www@Enter-QA@Com

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