Going Postal. Trippy, funny, dark.
Snuff Box. Comedy about hangmen. What's not to like? I wish there were a thousand episodes.
Spaced. Simon Pegg, a bunch of wonderful actors, and more sci-fi references than you can keep up with.
Black Books. I wish I was Bernard Black.
The League Of Gentlemen. A show so strange and funny you can smell it.
The Inbetweeners. If I were British, I would be this uncool.
Peep Show. Mitchell and Webb are an amazing duo, watch also for "Mitchell and Webb"
Shameless (UK Version). Loved it till the McGuire's took over, but it's still good. Scatter!
Hyperdrive. Like Red Dwarf, but with more contemporary comedians like Nick Frost - the other half of the latest Simon Pegg movies..
Assuming of course that the IT Crowd, Little Britain, etc, is all known as wonderful, of course..
To be honest there are very few shows from the past decade (i.e. not Benny Hill, not Fawlty Towers) in the "British Comedy" list on Netflix streaming that aren't good.