As everyone else has said, the most sensible option would be to get something that abit cheaper to insure. Your own policy on a mk5 GTI will be well over 5K, you'll even be getting quotes for double that.
It will DEFFINATLY be cheaper on your dads name, depending on how many years no claims your dads got, you may even get a quote for under £2-£3k, if your mums got alot of no claims stick her on there too! HOWEVER this is illegal, as someone mentioned its called fronting. If you get caught they will void your insurance and it will mean you've been driving without insurance and you'll get 6points and a 12month ban, you'll have to take both tests again too. But thats if you get caught, ofcourse.
Saying this, the insurance on any GTi is going to be expensive, i know how you feel because you've just passed, im only 20 so im still young, there was a time where mummy and daddy paid my way too, i had the best car when i was in sixth form, now im at uni in debt, still got my motor though, but could do with the money. Most normal people will say you should save the money, this is the best option because it will deffinatly benefit you in the future, especially in times like this. But your only going to be 17 once mate and its alll about the way you feel when your driving! - Just saying how i feel!