The £500 deposit is fully refundable and should be requested. A discretionary deposit is nothing more than a statement of intent as the car is never owned by the customer, so there is no legally binding agreement. The actual order and contract is with Motability Operations. The dealer will be able to switch another customer into that order slot (if the order has actually got that far) in a heartbeat and if they can’t another dealership awaiting build allocation slots will bite their hand off. The dealership will suffer no financial loss as a result of the cancelled order so has no right to retain the £500.