If we didn't have to offer a warranty lets think what would happen. Main dealers would rent a big field and sell all their P/Ex's to the public or the public would flock to BCA. The independents would have there stock supply cut off over night.
We can spend £400-£500 easy on mechanical recon on most cars add our profit onto that and you could be trying to sell a car for £1500 more then is advertised in the Main Dealers 'Part Exchange Field' .