OK folks
James Bond is definitely British, therefore the actress playing "Jane" Bond should also be British (or at least capable of a realistic accent - Gwynneth and Renee are the only Americans I can remember doing that).
There is also a need for experience, a knowledge of life and a sense of mystery. Sean Connery is (IMHO) the role model and Pierce Brosnan comes in second.
Keira Knightly is just too young and fresh. She would be unbelievable as a trained killer who graduated with a First in Oriental Languages from Cambridge and went on to be a naval commander, let alone a special agent "licenced to kill".
I can't actually think of a well known British actress who would fit, at the moment. I thought Halle Berry did a very good job as the most actively involved "Bond girl" to date...but someone like Uma Thurman (Kill Bill) has more credibility as a killer.
I'd say that Jodie Foster has the right attitude - I found her very impressive as the underhand double-dealer in "Inside Man". She's about the right kind of age as well.
KP