Ebay is shit!. They removed a listing i had because i said "I reserve the right to end the auction if it sells elsewhere". They didn't email and ask me to revise it they just cancelled it, so i lost everything that was written about the item which took me about an hour.

Anyway, i wouldn't take an ebay sale as a sale. Although he's entered an "agreement" to buy its not really a law binding deal, he has the right to test drive and listen to the engine just like any other buyer from autotrader or something. Whats a negative feedback in comparison to say £1000 down the drain because you didn't check something properly.
I'd say if you give him bad feedback he'd just say you wouldn't let him listen to it like you had something to hide and you'd have no chance or reselling.

If i went to see a car with a view tyo buying it and the guy said he wouldn't start it up i'd be gone.