I believe people have had theirs retrimmed for closer to the £500 mark. Lomoto for one has had a stunning retrim done. Not sure on the exact price of his but they do look good.
The other option you have is to get some aftermarket seats secondhand then all you would need to do is get some 350z subframes and swap them over. I got some Bride subframes from Adam and after some messing about, got my Cobra's installed nicely