Reckless Records on Holloway Road, Boot sales at Camden Market, ask for Gerald. Go to Blow Up's parties and ask the door girl or go-go dancer. Look in the directory pages under CD's then see if they advertise lp's. Look in Time Out London. Here's a big help for the same question: www.blowup.co.uk
This is my favorite record store for soundtracks and vinyl, period:
Intoxica Records. That's all the info I'll give you because I like them so much. Now you find em yourself.