Be careful with small ads 

If you buy a used car from a reputable dealer and it turns out to be stolen, there should be no problem. 

• Be cautious with small ads. Go to the seller’s house – to make sure he or she lives there! Check that the car’s chassis and vehicle identity numbers match those on the documents and that the registration document hasn’t been tampered with. 
• Be wary if the seller can’t produce the registration document, though he or she may have a valid excuse. 
• If you buy through an auction, take advantage of indemnity clauses. A small fee is charged but you are protected should you find you’ve bought a stolen vehicle. 
• For more information on buying a used car, you can visit the AA Car Buyers Guide or the RAC "Buying a used car" page