Just get a credit card with 2years interest free (longest I can see at the moment is 20months), setup a direct debit and you're all good. If you haven't paid it off in time then just balance transfer at the end of the period onto a 0% interest balance transfer card, current longest on those is about 34 months. There will be a 3% fee on moving the balance between cards but basically you're looking at close to free finance for nearly 5 years.
If you can't get a high enough credit limit to put the whole lot on CC, then you will have to do the old fashioned route of saving the difference between the credit limit and the car.....or set your sights a little lower.