I get interest on my money, Eddrach, more than some finance companies charge, for example Vauxhall is offering 0% finance on its new cars.
You need to shop around, haggle and make sure you know exactly how much the car will cost you before you sign anything.
Finance companies give the car dealers big cash backs when they sell a car on finance, which is why many dealers offer better deals when you sign up for credit.
One way to beat the system is to haggle on a finance deal then cancel the finance within 14 days. There is no penalty, the finance company have to accept the full amount of the price of the car before interest etc is added.