HMV oxford st used (not long ago) used to have a decent dance section.  Infact, in that shop vinyl used to occupy the whole right hand side of the ground floor (a sizeable area)- but has now shrunk to a far smaller area at the rear.  Same thing in Virgin.

Yes, I KNOW there are better places for dance music (Junkies, Sounds of the Universe, Reckless, etc) but that wasnt my point.  Infact, those kind of shops have been dwindling, too, such as Atlas a few years ago.