[humph]

Sorry no good news here. I have been in this situation before, and the one where I have bought a car in a lower insurance group and have been met with the same attitude. In fact my previous insurance company tried to charge me an additional premium!!!! If you move to a riskier area then they will be the first to demand money, but are unlikely to refund any. You could cancel, pay the compulsary fee, and move to another policy. But you will lose your NCB for the part year.

Are you sure the new postcode is "better" than your last? I remember a link being posted on here to the offical insurance company ratings for postcodes. Will see if I can find the link.