I know the feeling! It is beginning to change with some companies considering offering a "better" NCD on the 2nd car if you are insured already with them (I think Directline are starting more of this with their "MATCHED NCD" etc). Don't know of any "off the top of my head" who would insure a mad hatter like a tuned GT-R and do this although .
I insured my R33 GTR with them and they mirrored my 9 years NCD, without affecting my current 9 years NCD on my other car which is with another insurance company. And I was a first time Skyline and Import owner.
This was after me trying A. Flux, who, having initialy agreed to insure me on the above terms, refused to do this point blank and also A-Plan, who just were not interested, in fact they never even bothered getting back to me in the end
MCE will also take an agreed value, and their operators are very well informed, not only that, they are extrememly competitive (in fact cheaper than A. Flux before A. Flux realised "their mistake" in agreeing to my NCD).
I'm with and been with MCE(3 policies) for years and I think I was the first skyline gtr they ever did many years ago when they were called elite insurance advertising in Top Marques, As they didn't know what it was and had to leave links and pics to show them, To which they do them now.
They are easy to deal with and you can get through on the phone quite easily, Unlike some other insurace that keep you on hold for hours.