Pay for the deposit on a credit card.
I will repeat. PAY FOR THE DEPOSIT ON A CREDIT CARD!
Under the consumer credit act, if you pay for any part of a purchase of between £100 and £30,000 on your credit card, the credit card company has joint and several liability for the entire amount.
That means that if the car does not meet the standards set by the sale of goods act, you can get the money from your credit card company. Of course, it is best to exhaust the possibility of getting it sorted with the car dealer first but you are then not risking losing everything you have paid should the dealer decide to go into liquidation.
This seems to be a popular tactic by car dealers to avoid paying money they owe.
Don't believe me? I now have a settlement offer for £9711.68 plus insurance costs from my credit card company for a car I paid the £500 deposit on my card for. I paid the rest from my debit card.
If the dealer doesn't take credit cards for payment, Perhaps you should ask yourself why
One more thing - the car's fault was that about once per week/fortnight, it wouldn't idle properly. The fault would clear within a few hours. There were 3 attempts to fix the fault unsuccessfully. I requested, then demanded a full refund. The dealer disagreed.