There are quite a few sites which are willing to import Skylines for you if they don't have it in stock. I imported my R33 GTS4 from
www.bestjapancar.com which currently has a standard GTR V-spec for about 15k. Though there are a few more like
www.mvi-services.com and
www.northwestimports.co.uk (which is based in the uk and got showrooms in the north). These are the ones I know about and there's bound to be more if you look around.
Firstly it's not difficult at all to import cars if you have an agent to import it for you

. Allow about a month for the car to arrive and about two weeks for conversion and SVA test.
The thing to remember is that you'll need to add about 2-5k more to what ever the price is quoted to you on the website in japanese yen, that'll include shipping (£700-800), vat +custom (about 20% of car price and shipping ), conversion (about £500 for collection from port and fuel pump, rear fog light, speedo uk coversion and SVA tests etc), then you'll probably want alarm (£300) and anti-rust oil/wax tratment (£70-80).
If you do go through the websites I looked at above, they'll all manage the whole business of deregistering in japan, shipping, collection from uk port and conversion for you so it's mainly painless.
One drawback is that you cannot see the car and there may be some damage during shipping (mine gained a huge envy scratch on the bonett during shipping) and that it's a leap of faith to paid a large sum into some account and hope for the best. But the sites I mentioned above have all been around for some time and should be fairly reliable.
Hope that helps
Min