You may receive a winning bid from a person from a foreign country and they wish to buy your car. They wish to pay via cheque and are willing to wait for the cheque to clear before going to collect the car.

They will also overpay you on the cheque and ask that you give them the extra back in cash when they collect the car. So if they bought the car off you for £2000, they will send you a cheque for £2500. They will say it is an error and rather than issuing a new cheque, they request that you give it to them in cash when they collect the vehicle.
Unfortunately several weeks after the car has been collected and the cash handed over, you will receive a call from your bank saying the cheque has been reversed and the bank will take the payment back from your account.