This year's nominees don't appear to have that overlap problem (see the full list here), which could very well mean the Circle has changed its rules since last year. Either that or there really is no clear enough front-runner this year in any of those categories. Or maybe the Circle just felt there were too many non-British films, directors and performers worthy of notice and didn't need to exclude any of them just to spotlight their own movies more than necessary. The one interesting thing is that while Daniel Day Lewis could be considered a British actor, he is only nominated in the more general Best Actor category. Also, it is interesting that Paul Greengrass is nominated as best British director for The Bourne Ultimatum, a movie nominated only in the more general Best Film category.
The best thing about having the British-only categories is the recognition the LFCC gives to terrific films like Control and This is England, which aren't on the radar enough in America to be given notice here. Also, the British-only directing category allows for the general best director nominees to include other foreign (non-American) directors like Cristian Mungiu (4 Months, 3 weeks, 2 days) and Florian Henckel von Donnersmarck (The Lives of Others).