[MADSTA]

The Thick Of It
The Thick Of It
The Thick Of It
The Thick Of It
Peep Show
The Thick Of It
The Thick Of It
The Thick Of It
The Thick Of It
The Thick Of It
The Thick Of It

[MADSTA]

Originally Posted by Cody Nelson

Also, though they're not sitcoms at all, these need always be mentioned in discussions of UK comedy:

QI
Would I Lie To You?
Never Mind The Buzzcocks
Mock The Week
8 Out of 10 Cats
The Big Fat Quizzes

Mock The Week is probably one of my favourite shows ever. I like to call seasons 3-6 the "golden era" of that show, I miss Frankie and Russell.
NMTB is great too, though I haven't watched it in a while. I find some of the hosts are just awful, I wish Simon Amstell was still doing it.