If you know anyone who has dealings with a motor factor or car accessory shop they could find the vin number or, more importantly, they would be able to give you full spec on the cars.
Of course they may not want to!
I would not be happy if there is a publicly available Reg to Vin. I know there used to be some spare parts and insurance sites that “leaked” the VIN when you looked in the source code. But if there was a general side this would make it too easy to clone a vehicle.