Hey there bud im a young Z guy myself and trust me 17 is not a good age to get one, i know you think you are getting a good car out of it and all but you have to start at the bottom and work your way up! I started with a Mk3 Fiesta then a civic. Last night i drove my friends 200SX which is putting out 230 BHP and that was very hard for me to believe the amount it could pull, the 300 on the other hand has so much more power than this and it will do alot less to the gallon. A Zed will do about 20 mpg, you think you can afford to run it?? So to put that down that is about £5 everytime you drive the thing.
At the moment the insurance for me is £1355 on Third party & Theft, 10 months with elephant.co.uk (part of admiral). I'm 20 years old with full uk driving since oct 2006 with pass plus and 1 years no claim. I have put money aside for this car because i know what it is going to be like on fuel (about £60 a week driving it normally).
Just thought this would help you out!