I'd just like to add one more store for UK - PicStop. It's actually recommended by Fanjita himself, in a February news post on his site. Here's there best prices -

128 MB - £15.90 (why this is the same price as the 512 I have no clue, other than this is Sony and the rest Sandisk)
256 MB - £14.90
512 MB - £15.90
1 GB - £17.90
2 GB - £39.90
4 GB - £59.49

PicStop Homepage

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