I heard a radio adaptation of one of the Guards books on BBC 7, probably guards guards, and it annoyed me. Vimes wasn't grumpy enough and was portrayed as a bit of a "Earnest Copper". The whole point is that Carrot is the earnest copper, and Vimes is the disillusioned cynic. And the Patrician was a bit too much like a slimy local councilor, not nearly menacing or subtle enough.
Maybe it's just been a long time since I read the early books, and the characters changed over the intervening couple of decades. Guess I'll have to dig them out for a re-read.
PS - Sandman - yes that would be good. Except it would be hard to figure out how to get his voice right.