Where in london can i buy a cheap and good brand of compact flash card for my digital camera.?

I can find some good deals on the internet but since i;ve never done it before feel things wont work out proper.Im looking for brands lik Sandisk or Kingston,Lexar, or any good brands.
So i want to go personally and buy it.

I want to go personally and buy it at a shop.

I'm a professional photographer and I buy my CF cards from EBay just the same. Please don't get sucked into the latest high speed cards because you won't need it unless, like me, you are photographing motor sport at seven frames a second. Go for the older series cards which are for 99% of people just as good. I recommend either Lexar or Sandisk, have both and they work fine. Kingston are I am told just as good and make the RAM for most computers including my Dell. After all, a CF card is but a separate hard disk.

Have u tried Ebay?

Tesco, Asda and Argos are all doing good Xmas deals at the moment.