Sorcha,
Treading on dangerous ground when you try and place the accents to the characters (what accents do Russians see Orcs as having?) - though your choices could fit! I agree with Malcolm re. Hobbits and rural, I'd have placed them more with a Somerset accent, however.
As for a great book with loads of imagery moving to screen - 'tis always a risk. I never thought Gormenghast could be done (actually I always prefered this to LOTR). The BBC did a marvellous job on this (so I thought) and so indeed it can be achieved. From the clips on the web page it seems LOTR might also achieve this but we'll all have to wait and see.
Actually this all raises the comparison of "imagination" vs. "realism". I will always prefer Dr. Who (with its hokey sets) to the likes of Star Trek (all generations) which seemed to have more money to spend. The story lines in the former seemed so much more imaginative. But then again that's another thread maybe on another site.
Rana