Not a kept secret in England. Not really even a kept secret in the states anymore. The ladies swoon over Cumberbatch, and he's turning into a big bill actor. A good Cumberbiatch knows he was in Sherlock. Not dissing the show though, season 2 was phenomenal.
But if we're going by those measures:
IT Crowd is a good british comedy.
For my money, it's "Raising Hope" and "Jeselnik Offensive" all day. I don't think how people realize how great (clever?) of a show Hope is unless they give it the time. It's hard to be THAT feel good, and somehow engage the audience/actually be funny.