Yeah he's a master of it. It's so funny, too, just that tone and accent. He obviously has made a career (well..two cult british comedy shows isn't quite a career but you get me) out of it.
GOB: I'm an ideas man Michael; I think I proved that with *beep* Mountain
On the Mighty Boosh extras, his voice is less deep and when he speaks it's quieter. I heard in an interview with him that he got his voice from watching those types of bad drama's as a child and realising that the actors in it originated in theatre so when they got to television, thier voices were always booming due to them having to project in a theatre.
Love Matt Berry's voice, he puts it to good work on everything I've seen him, everytime the Volvic advert comes on tv too I'm there listening to him lol
I'd agree with the earlier poster who said he sounds like Basil Expedition (Michael York). If you watch Austin Powers or Logan Run, it sounds pure Sanch - or rather Sanch sounds very Michael York.
The actor (Matt Berry) uses the same accent in pretty much every thing he does, and always plays a fairly similar character. Watch him in The Mighty Boosh and The IT Crowd.