Tobe, if you don't mind my pence...
firstly, dont do the "mum's insurance" thing, i know two people that have been done by the police for it. it does happen
secondly,i was the same as you a few years ago. my advice is, Don't do it. get a non GTI car, spend the money on something that accomodates you age and your wallet. i made a 106 diesel, a GTIalike when i was 18 cause i couldn't afford the insurance on GTIs. after i binned that lovely car, being young and over confident. that stinked me because all i could afford was TPFT! pennyless i bought Golf MK2 1.3, i loved that car and over a few years i've worked my way through powerbands,Astra, BMW 325, Civic Type R, girlfriends MX5 taught me a lot about road handling. now i've finally bought the MK4 turbo i always wanted. its no less special cause i waited. but it will be more rewarding cause i can enjoy it to the full after a few years of experience.