The VVT has no advantages to performance, it is there purely for emmisions as far as I'm aware. It was introduced in the golf 1.8T's from 2001, but the 2001 golf 1.8t is an AUM engine block and different from the ones fitted in the
Ibiza Cupra. The Leon cupras had VVT though, as Mork said.
Oh and I think the low mpg is more to do with my right foot, it can get early 30's mpg when I want it to lol.