You don't get the Solenoid with it you know, so you'd have to have the Blitz SBC ID3 already or whatever other EBC comes with the dual-solenoid.
I'd really recommend sending this guy a message, he's 150% legitimate. I've bought a load of stuff from him without having an ebay sale to back me up should it go wrong. I think I paid about £180 for my MMD.
Nengun are pretty widely known within the UK jap car community, my brother has purchased some stuff for his GTR from them and they have always been reasonably efficient.
If they have what you want in stock then I would not hesitate to buy from them.
You might also want to have a look at http://www.greenline.jp to check prices- although they probably won't be any cheaper.