I’ve used the following quite a few times in the past I these foreign non buyers.
Mr Customer.... if you were in the market place for a parachute would you be looking for the cheapest ? No you wouldn’t, you’d be wanting to buy from the most reputable source with the best reputation, the best quality, the best prepared, the best folded to ensure you have a safe landing, it’s exactly the same when buying a car. Your priorities are wrong if all you are looking for is CHEAP.... if you buy CHEAP you pay twice....
As all my cars are “buy it now” via a nominal fully refundable deposit upfront, only pay balance when happy, nowadays it’s very rare I get asked.
If someone does politely ask “is there anything I can do” then I’ll usually will give them £50 worth of fuel, they’re usually very grateful for the gesture.