British comedy hasn't been that great for a little while now. I'd say that right up there would have been Monty Python, Harry Enfield and Who's Line Is It Anyway? - I assure you, the British version is so much better than the American version.

Also, "You're an idiot, aren't you?" isn't funny. It's an insult. The "aren't you?" bit isn't supposed to be funny either. Maybe it was the context it was used in, but on it's own, that's not a joke as far as I know.