hmmmm just read this from autotrader website....

If you’re buying a vehicle privately and it’s later identified as stolen you may have no right in law to its ownership. Follow out tips to help you avoid becoming a victim of car crime.

View the vehicle at the address shown on the registration document
Ask the seller for proof of identity - make sure the person selling the vehicle has the right to do so
***Never buy a vehicle without a registration document even if the seller says it has been sent to the DVLA for changes***
Check the vehicle identification number (VIN) corresponds with the number on the registration document. This number can usually be found on a metal plate under the bonnet
If the VIN plate has been removed, ask why
Ensure you get a landline number – not just a mobile number
Check the locks on the car and make sure they do not differ (thieves often change locks they have damaged)
Check the mileage reading corresponds with the service history and past owners

Not sure what to do now seems a dodgy area this does.