I am sure supercardstore.com does have R4 and is UK based
Anyone thats selling the R4 in the UK will be charging an arm and a leg for one. I got mine from bamboogaming
http://www.bamboogaming.com/index.php
At the moment it costs £16.69. It might take over 2 weeks to arrive but its a lot less than you'd pay in the UK for one.
I'd advise you to stay away from any one such as the addict, he might be a genuine guy or he might be just a guy looking for a cheap buck. think of where he would have got them from... and why he wouldn't have a "normal" online shop that he'd link you to if he needed to sell online.
too good to be true... probably is.
if you could see what has happened to some unfortunate fellows on the trading forums (with a member +100 posts mind), you'd see what I mean.