Why spend money? Speak with the vendor and is the car has full service history and the cambelt etc and usual items are said to have been covered, ask for the details of the garages where the work was done and call them.
Ask for the vin and mot details to do a mileage check and it will detail advisories too. The garages where the thing's been looked after will be able to tell you anything out of the ordinary. If the vendor won't play ball, I take the standpoint that they're trying to hide something and I walk away. After all, all they're providing is the service history which you would see anyway.
After that, go see the car. take ur laptop - if it takes ur fancy, HPI it once ur there.
alternatively, do the research above and then pay the RAC to check it over for you.