I just bought mine on wednesday, and I'm picking it up on monday. I've been worried about this all week. I just thought things went way too smooth at the dealership. I got the car at a great price on the S plan, and they told me I qualified for 0% financing. This is a common scam they pull. They knew you didn't qualify for the 0% when you first bought the car. But they told you you did to encourage you to take it. The contract you signed actually has a clause in it saying that the deal isn't final until your credit is approved. How did you put your deposit down? If you gave 'em a check, it will be a little difficult to get back. If you paid by credit card, drive back there, drop the car off, and tell the dealer to shove it up his a$$. They will be pretty pissed about having to sell a car that has a few hundred miles on it, and has been registered with the DMV once already.
I won't take the car until I have the coupon book in my hands. That's when it is final.