Thanks for the feedback, so 16"s it is.
I have no intention of putting 14"s on a GTV, that was just an example. I just happen to have access to some 15" wheels which I was hoping I could use temporarily, but clearly not. Steels tend to offer more clearance than alloys as thinner sections used.
It's fairly common in VW circles to have a set of smaller steel wheels (G60 spec) for winter use, to save damage to expensive split rims etc.
The small/wide wheels look has come from the Japanese I believe. Personally, I like the look, but haven't done it myself as it wouldn't fit over my brake setup and I use the car daily.