Firstly decide what you want out of the wheels, if pure style then 17"s are my reccomendation, but if you want to retain some aspect if performance go for some 16"s (OZ alloys are very light weight).
However it also depends if you want a low car or wheels to fill the arches.
Personally i prefer 16"s as they are a good compromise on style and performance , as 17"s on a mk1 wont just go straight on (beleive me i did the same), when i lowered it -35 mm on pi suspensin kit it rubbed, full lock was non existent, can knacker up wheel bearings, you need to trim the front and rear arcg aswell as removing the arch lining, and if your very unlucky you may need the arches rolling!
Hope this helps!
Cheers
Anthony