What is a Food Fiend to do in London?

Hi all! I’m in the midst of planning a two week trip to London over the Holiday season, and could use some help in finding food related places in the city that are worth going to. I’m not just talking about restaurant recommendations here (although those would be appreciated), but also specialty shops along the lines of say, Cybercandy, Books for Cooks, and of course, Harrods.

Any recommendations do not have to be of a quintessential British experience, but they would certainly be appreciated. For example, I’m just as happy finding a good kosher deli as finding a great place for an English Fry-Up.

And yes, I know this may seem a bit premature, what with the trip being three months away, but this is my modus operandi when planning long trips. It gives me additional time to look forward to my journey.