Well if you've only seen one ep of L&O:UK with Freema compared to 18 episodes of DW with Freema (not counting 3 eps of Torchwood too) then I should think you had got used to Freema's accent when playing Martha, but not yet got used to her accent when she's playing Alesha.

As for Sherlock, the first episode (written by Teh Moff) is far and away the best of the three.