at 17 got my 1.4 Mk3 golf insured for £1100 tpft, that was with alloys, if you phone compaines up and just say that you have locking wheel nuts etc then usually the price of alloys dont make it go up, the price will soar up for lowering your car though, i know you want it to llok nice but it really is best to keep you car standard at a young age because insurance companies just htink boy racer and your insurance rockets.
I'm coming up for 19 soon and then on my Mk3 my insurance will be £500, and for a Mk2 gti with martin it'll cost me round £1400 tpft, Your better off waiting a few years mate