Have a look at this press release from the BBC. It announces the casting of:
I am delighted with the casting of Jodhi May as Mrs. Weston. I thought she was amazing - and absolutely beautiful! - as Mirah Lapidoth in Daniel Deronda. As for the other two actors - I can't say I've ever heard of either of them. . . although apparently Robert Bathurst plays one of the characters in an old version of Wind in Willows that I've seen. . . not sure if that really counts, though. Anyways, they both look right, which is good, of course. BUT JONNY LEE MILLER TOTALLY DOESN'T LOOK RIGHT AS MR. KNIGHTLEY!!! *Sulks* Why? Why, why, why did they cast him as Knightley. . . :-(((
For a more complete, comprehensive, coherent post about this, head over to Old Fashioned Charm. You could also check out the post at Austenblog.
(angry with the BBC for casting JLM.)