Used CD shopping in London ???

Will be in London this weekend - anyone know of any good used (or selling new stuff cheaply) CD shops - my tastes are quite wide - rock (all shades), metal , pop.

I already know of the Music and Video Exchange shops but I think quite a few of the others I have visited in the past have gone by the wayside e.g. Sellanby, Steve's Sounds, Mr Cd etc...

Anyone know if Zodiac (only opens on Saturdays) is still around in Wandsworth ?

Any help appreciated.