I agree about Julia McKenzie's superb acting. I actually felt for her at the end, she'd obviously been completely oblivious to her horrible husband's lecherous ways.
I also though Keeley Hawes played her character well, especially in the last episode.
On the whole, though, I agree with Jane10's feeling that there was an odd, unpleasant atmosphere throughout this series and I'm glad there won't be a sequel (fingers crossed!)