I've used Renchi.com a couple of times (though for games only) and they did fine. They do have a white 320GB PS3, though it's the HK version, for ~ £248 ($399). As far as I see it the only potential problem getting that one would be DVD Region 3.
Now, Japan is Region 2 just like Europe, but it's NTSC. I'm not sure EU DVDs would work on a Japanese region-locked player (PAL region-free ones don't work on my US Playstation 3). Still, you might want to look into that if this is going to be your DVD player.
Renchi also offer to mark down when you shop, so that custom fees will be lower/none. I do that for games, but I'm not sure it's a good idea with a console.
[edit: Yesasia might not cost you much more actually. I've bought games and manga from them and they send them to me from Germany, they must have some shipping centre there. So there is no import tax.]Please ignore, apparently not for Sony products.
