Tim, writers will always be the key to success, even in reality humour, cause someone has to write the plot and scenario
Still, I'm not impressed with the current sitcoms. Outnumbered and Inbetweeners rely on kids, which is OK but doesn't make me laugh that much. I remember actor Dennis from the 90s in Newman & Baddiel? With the famous "That's you, that is".
Benidorm has a good idea but no timing and meaningless long scenes (one in the bus). Beautiful People about a gay teenager has bad acting and is the least funny of all. The The Thick Of It is out of my reality since I don't live in the UK I don't follow local politics. I enjoyed Yes Prime Minister and Rick Mayal's The New Statesman in the Thatcher 80s, but this one is too early to make history.
All in all, I can decently say that the last relatively good British sitcoms made were Ricky Gervais in The Office and Extras series, Ali G series and The IT Crowd still running.
luis