look mate, regardless of what some people might think. the car is mint. end of.
i bought it without an hpi check, as i took the guy to be trustworthy. also i never even asked if it was cat d or the like so in trading it in i paid a price.
however, i never had one problem with it. all work was carried out when it should have been etc. it is a brilliant car mate, and if i could afford the cup and the meg i would still have it.
so on that basis, buy it and dont worry bout it.
now though, you are only 17, so insurance is gonna be mega and i mean mega on a 172, never mind a 172 cup.
if you can afford to do it, then do it.
but as has been said, dont cripple yourself financially for it. as as with any car, anything you put into it, is money you will not get back.