Ben,
Similar situation with me at the moment. Needed to insure 2 vehicles but the insurance company would only allow my 8 yrs NCB to be used against 1 vehicle and the other had to be under a seperate policy, they did offer me 1 years NCB as a good will gesture due to being an existing customer.
The way round this situation - for me anyway - the wife is a named driver, fully comp cover as I am on the vehicle 1 policy. Vehicle 2 is now insured under her name with me as a named driver, fully comp giving me the same cover as her.
The wife - no NCB - through a "women specialist insurance comany" insured the vehicle for half the cost that I could with no NCB.
For the same vehicle and same policy terms, her cost with no NCB is almost the same as my cost with 8 yrs NCB - rip off insurance companies as far as us men are concerned.
Women drivers huh !!!!!!!!