hey can claim it was a binding contract and they never said the deposit was refundable, you can claim you were told it was refundable if you don't want the car, so it's going to be your word against theirs. If they are happy to p*ss off a potential customer and get some bad press they may fight it, but only if it's worth it to them financially. Threaten them with the small claims court, it's simple to register and start the process and costs a few £s it's online via a government website. If they win, you only pay the fee, if you win they pay the feee and you get your money back for the deposit. You and they cannot charge the other side of r solicitors, but can you imagine a firm sending somebody who isn't a solicitor to represent them? No. They send a solicitor, the cost will be IRO £200 / hour, including prep work, and your costs will be, turning up.
So assuming they win, and you put up a good fight, it's not going to be just an hour or two of prep and a couple of mins work, so they're going to be out by IRO £500. They could look at offsetting this by the deposit you paid, so they may be in / out of pocket a bit, and you'd be out by the deposit and the cost of turning up and the fee.
If you win they loose the deposit, loose the fee, loose the sols cost as they cannot claim it from you, and get some bad press assuming you go to the local rag.
They are in a pretty much loose- loose scenario. You have a chance of coming out OK, and that normally scares a big company into just doing what they need to to get rid of the problem. In this case, refund you the deposit.
Get the paperwork, fill it in. Take it to the manager of the dealership and have the normal discussion about the fact the verbal agreement the refund was refundable is a verbal contract and just as binding as a paper one (the only time that rule doesn't apply is for sale of land) . If at the end of it he / she says No to the refund, ask him / her to look at the contents briefly and sate you're going to start proceedings within 48 hours if you don't hear from their head office with a satisfactory response.
Make the F***ERS sweat.