I have just done the sums if you save up to buy a £10,000 car and say it takes you two years to save you will probably receive £500 interest from the bank whilst you are saving, therefore a car will have only cost £9,500, or the other alternative is you could use the £500 to upgrade slightly. If you buy a car on tick, the car over three years it will probably cost you £2,500 interest therefore costing £12,500 plus the admin fee that they like to tack on.
That is a saving of £3,000 on the cost of a £10,000 car. Which means, assuming you keep your car for 3-4 years after about 10 years you will have a free car because of the money that you will have saved on interest. Brill!!!!