How far to the nearest road where you could leave it where it wouldn’t be obviously pissing off any residents? ‘push’ it there and post the bloke the keys? IANAL
I’ve had similar – bulky item paid for and then not moved for ages – problem is it’s now their property and you are the caretaker (ie possibly liable if say you did roll it into the sea) – to deal with it you need a ‘charge’ (reasonable to a court) to off-set the cost – so for example you write via ebay (doesnt matter if they dont respond, you have it on record) that the car now needs to be removed and the removal quote is equal to or higher than the cost of the item and they have 2 weeks say to collect the car otherwise they will owe you money to cover the cost of removal etc – it worked for me but they did turn up in the dead of night on the last day.
Assuming he’ll need to come to you to get the key then you probably need to be slightly bothered as you’ll be sitting in the house doing not a lot waiting…
BitD my old man sold his old car to a guy at work who then disappeared. We just held on to it and it was my learning hack until a Range Rover lost control in the snow and smacked it into a neighbours garden. My old man just kept winning with this car, sold it for good money, the insurance paid out good money, he then bought it off of them and we stripped it and sold all the parts.
About 10 years later he turned up as a Bristol City Councillor on TV. He never came back for his cash or car, odd people out there