Mitchell & Web Look was on Netflix for the longest time. I stopped using the service so don't know if it's still on there.
I believe every episode of Unbelievable Truth, Mitchell's radio trivia program, is available on Nick from Fulham's channel. If you aren't subscribed to that channel yet, you should be. I think he has a lot of Mitchell & Webb Sound as well. Though, of course, you should be buying it from iTunes.