Hi DavidG and welcome to the forum - if a little belatedly ...
The insurance racket is a little difficult for anyone with a modicum of logic to follow and I have to agree with many who believe that NCD is NCD and should be driver-related and not vehicle-related (watch RED ARMY jump at this one).
Basically NCD is accumulated on a per vehicle basis and can only be used on another vehicle if the policy is surrendered. In other words, the UK system currently states that each vehicle earns its NCD status NOT the driver, however if the driver makes a claim on one vehicle it IS taken into account an all policies, so this is a clear case of the insurance market having their cake and eating it.
So, you are right, if you have one vehicle that you have driven faultlessly for ten years and you then buy another, it is completely unreasonable that your driving record is not taken into account and you have to start from scratch with another vehicle. That, however, is the way that the system is set up and I'm afraid it is unlikely to change. I have often tried to explain that I can only drive one vehicle at a time, and therefore it is ME who earns the NCD and NOT the vehicle, but I'm afraid I do not have the money to challenge the legality of the insurance world in court to prove the point.