Not sure if I should blab about this (as I usually prefer to keep my opinions to myself...), but I've been a user of autorola's Autofind Stock Locator for many years. Not only does it have a large no of main dealer cars for sale, there is also a facility to add cars to advertise. Doing this by reg no lookup gives both cap and glass valuations. Tbh, I don't think I pay anything for it, so seems like a proper bargain to me! If there is a cost, I'm sorry but don't grass on me.