I haven't read the sequels authors have written I'll have to look them up for you as I can't remember them. I think from memory one is called 'Mr Darcy Takes a Wife.'
I have read 'Mr Darcy's Story' which is Pride and Prejudice from Darcy's point of view and that's pretty good.
I have not read all of Austen's book even though I have them all. I got about halfway through Emma and dumped it annoyed that she comes across so dumb especially when it compared to Elizabeth.
I too love the BBC production when I saw the previews for the Keira Knightly version my first instict was Darcy's so scruffy! I mean come on Darcy's meant to be the perfect gentleman.