I looked through this entire section (and the other interview thread) and couldn't find this radio interview of Benedict anywhere (but it doesn't mean I didn't miss it - apologies in advance if that is the case).
It isn't exclusively BC but about the 11:43 mark his part begins (and goes to about 17:46). Mark Lawson interviews Ben in his show Front Row as one of the names behind the arts headlines of 2010.
The interview centres generally around his role in Steven Spielberg's War Horse. He talks about feeling rough the first day on set and about learning to ride (he has such a flowing narrative way of talking - every answer is like he is telling a complete story). He also talks a bit about playing in Terence Rattigan's After the Dance and how he had to change things between Sherlock's pilot and the 90 minute version among other things.
Personally I just loved listening to his "stories" (answers). When he speaks about his riding experiences as a 12 year old he seems to actually take the POV of the horse and it makes it such a wonderfully endearing way of explaining what it was like. And I love the little asides he does, like saying when he tells about going to a party on the last night of the play and staying up to 12:30... "I hope he isn't hearing this because I got to bed rather late".
And his imitation of Spielberg's voice is soooo good! He just launches into it naturally as if he is just hearing that voice in his head so it comes out that way when he relates the story.