I watch a lot of British TV, so I think I'm pretty acclimated to it. Also, Canada is more British than the USA (and I lived in the UK for a couple of years).
All that being said, I found The Office to go down pretty easily. It's the Northern accents that are really tough. I got used to them while I was living there. There's a show called Shameless that I got into there, but after being back in Canada for a year or so, I watched it again, and could barely understand it.
I like the silliness of UK comedies. I love Black Books and Boosh for that.