Use the fact that one car is £37,000 to negotiate the car at the Aston dealer down as much as possible. If he is keen to make a sale, he will first of all investigate the history of the cheaper car from central Aston Martin records and might find out it has been crashed or something. If not, he should be prepared to deal. If he won't deal, at least you should have some more information about the cheaper car that you would not otherwise have got. On the other hand, if he has the funds, the dealer might snatch the £37,000 car from the vendor, then re-offer it at £45,000. The best guys to tell you what it is really worth are father and son dealers Tom Hartley.