Sherlock Holmes's London - a quick question.

I'm useless at districts of London - being a provincial and proud of it, I never took the time or trouble to learn

Now, however, I need this knowledge for Sherlock Holmes and the Ravenclaw Codex. I'm trying to find a suitable place for the home of a well-to-deal dealer in antiquarian books somewhere in London, and I realise I have no idea where would be suitable. 

Any suggestions? If they sound slightly convoluted (the way Holmesian places tend to do), so much the better.