Where is 21 Grimmauld Place?

[Wendy]

bboy asked about possible locations of Grimmauld Place, and has 
received some great answers, but there is one thing I wanted to add. 
(I've snipped all the other discussion)

Steve, you might check with Lexicon Steve. He discussed the location 
of Grimmauld Place in his & Penny's Nimbus talk on the geography of 
Harry Potter. I did a quick search at the Lexicon just now, and 
couldn't find the information, so he may not have it up yet. But 
IIRC, he concluded that it was mostly likely located abou 20 minutes-
walk east (and a bit south) of King's Cross Station. I don't 
remember what all went into that conclusion, though, so I'd suggest 
you go straight to him to find out his reasoning.

:-)
Wendy