Garth Marenghi's Darkplace will always be my all-time favourite comedy. I'm surprised no-one has mentioned it yet, but I guess that shows how 'lesser-known' it is. Also, a sitcom called 'Ideal' which 'revolves around the eclectic array of characters who visit Moz to buy cannabis, socialise or both.'
The former is one of funniest spoof comedies you'll watch, everything about it is absolutely perfect. The latter is masterclass in making a very entertaining show out of a limited premise.