I love the Japan Centre in Piccadilly. It has a lot of great Japanese candy, cooking supplies, fresh sushi, hot food and bakery. It's my favorite Asian supermarket in London. I am going to go and try the fresh food selection.
Their new location is:
14 - 16 Regent St.
LondonSW1Y 4PH
UK
Click here for map to Japan Centre
This time I went in I bought a Japanese Grape Soda. I really liked it. In England they prefer blackcurrents. I've been fooled by so many purple skittles here that it's not funny. They tend to get different things in all the time. Last visit I had a melon flavored soda.
Everything from the sushi to candy is very reasonably priced and is well worth a visit.