www.moneysupermarket.com/loans/car-finance/
www.whatcar.com/advice/buying/car-finance-explained/
The best place to start is both of these places.
I have to say the claim that any car loan or finance can be guaranteed is highly misleading, and simply a marketing ploy that many lenders and car dealerships use to attract new customers - it goes through the same avenue as any other loan or credit where they look into your credit rating check and possibly other checks, to assess whether you can make the monthly repayments.
What do you want to achieve?
Own it?
Return the car to the supplier?
Trade the car in against a replacement?
You don't mind not owning the car until the debt is fully repaid?
The second link is best to help you with the decisions on what options you have. I am also in the same boat I don't have the money to fix mine but even if I did its old that I wouldn't want to waste more money on it.
I know I don't want annual mileage restrictions, I want to own it, I plan to keep it for a long time, I don't want to pay over the odds in apr because of the depreciation of the car it could mean the apr would make me pay a lot more than the car is actually worth.
I think I am leaning towards for a reasonably priced second-hand car with low car tax on a 0% credit card as I don't currently have a credit card they are all paid off and expired, it would involve dividing the payment over the time period so I would devise a fixed payment plan which means no upfront deposit. I will also have to factor in that insurance, tax and general running of the car will also run alongside this.
I have had 0% store cards and credit cards previously and have always paid them off within the period because the apr on these cards can be hugely inflated after the period has ended but there is also the option I could transfer the balance to another 0% card for a transfer fee.
It really depend on your circumstances, there is a lot to think about :(