I did near enough exactly the same this at 19 but worse. Luckily mine had a cooling off period which got swiftly used after my dad tore me a new ********.
Gotta love the people walking into this thread with an erection ignoring the fact the poor lad's been had saying 'Enjoy the car, ignore the rest" etc.
Smash it or burn it.
Too bloody right. If I took out this type finance deal I'd have two black eyes and my arm in a sling then he'd go to Car Craft and shove the keys up the salesman/woman with much force.