So, I was traipsing through the DiR community while at work today (very slow day) and happened upon a book written by someone in the fandom. It costs a bit more than I can afford right now, so it goes immediately onto the book wishlist. For anyone who's curious, this is it:
Four British Fantasists: Place and Culture in the Children's Fantasies of
Penelope Lively, Alan Garner, Diana Wynne Jones, and Susan Cooper
(Scarecrow Press/ChLA, 2006)
I'm also going to suggest that my uni's library add it to their collection (they seriously need to bolster the "on writing" section, particularly in regards to fantasy).