Japan Centre (Piccadilly Circus) - This is definitely one of the best places to go. The cd's are brand new and legitimate [look for the avex symbol]. You can also find calendars, magazines and more. Expect to pay up to £30 for a cd, £10-15 for a calendar, £7 for a magazine.
+ I found Rainbow, Duty, (miss)undersood, a-ballads, a song for XX and A best at Virgin Megastore also at Piccadilly Circus. (+ her German singles) A great store with lots of asian and international music!