In general, how long does it take for British TV shows to be released on Region 1 DVD's?

I’ve just gotten into the show Misfits and I love it. It’s available on Hulu, but I’ve absolutely fallen in love with the show and would love to own it. However, it’s not available for Region 1 DVD players and, short of buying a Region 2 player, there’s no way for me to watch the DVD’s. In general, how long do British shows take to be available for American viewing?