I ordered my 05 zed new with the Nismo Aero kit from the dealer.
It should be on the original invoice when you ask to look at the paperwork.
Assuming the prices for 54 and 05 were similar, brand new with the Rays and Nismo kit the original invoice should show purchase price of around £31k unless purchaser negotiated a big discount.
Another sign to look for is the factory fitted kit should be absolutely mint.
As for insurance, you will pay more with a factory fitted kit, but less than an aftermarket kit.
Looks like a lovely car.....hope you get it for the right price.