Changing cars on an insurance policy

[firman]

As per title really, looking at changing my car 6 months into my policy and my current insurer (seem to do more specialist, classic & 4x4 stuff) is coming out with some ridiculous qoutes.
Main question is am i going to have cancel my policy and not accrue any NCB on this policy and start a new one or is there a loophole that would allow me to buy the remainder of the policy and gain the NCB?
Probably a stupid question that I pretty much already know the answe to but just hoping the wealth of knowledge on here may know something I dont.

Cheers

Jamie