Recently purchased from a garage a Q7 advertised as having full service history. It transpires that the car has a partial service history. A car with a partial service history will surely have a lower re-sale value than one with a full service history. My question is where can reliable data source be found on pricing information for a car with partial service history and one with full service history. I intend on claiming the difference against the garage for mis-selling the vehicle to their financial benefit.