If I put a "holding" deposit on a car (for sale by a private individual) so as I can arrange a (leter) professional inspection, can I ask for my money back if said inspection reveals the car to be a "pup"?
The seller would have to agree to it. The only legal requirement he has it that he owns the car (or is authorised to deal with the sale by the owner) and the car is as described.
Most private sellers would agree to this unless they have something to hide.
However, they would be entitled to add a rider of their own - they will accept another offer and return the deposit if anyone else wants to buy it.
I would suggest that if I was the seller I would say no. Why should he accept the deposit? Are you expecting him to turn down a definite sale just in case you decide the car meets your expectations. And if it doesn't he has lost the other buyer. I don't think so. So what is the point of the deposit? Ethel is right though - some buyers might accept it, but you may have difficulty getting the money back if you subsequently walk away. Put yourself in the seller's position and think it through!!
I would certainly agree to return a deposit if an inspection showed any major faults. If anyone else wants the car in the meantime just take their phone no. The buyer has shown serious intent by paying for the inspection. Ethels answer says it all