I had one from a place like that a few years back. Yes, I did pay through the nose for it, probably double what I would have paid elsewhere but at the time I had bad credit and couldn't get a loan anywhere else.
Asking my parents was not an option (you don't really want your parents to know about your CCJ's, defaults etc!) and I needed a car for work, there was no time to save up.
It did cost me loads more but I had no problems with the Company in question and once that one was paid off, my credit had improved and I was able to get a bank loan for my next car.