The only thing that makes it illegal is that it wasn't printed by an 'approved' number plate manufacturer.
As I understood it, the law has for several years now required that the plate must be mounted at 90 degrees to the road surface.
A lot of E-Type Jag and Sunbeam Alpine, etc. owners whose cars originally had stuck-on plates had difficulties. IMO you've got no chance of getting away with it on a VX if they want to go by the letter of the law.
Would be happy to hear that this is no longer the case, but I somehow doubt it... since when has common sense prevailed with road traffic legislators?
Best of all is they don't have to have
any front plate in some US states. Suppose you could all emigrate to Florida or Switzerland where we have titchy little front plates. But, no doubt it's just a matter of time till we "harmonise"

with Europe and put snow ploughs on too! Bl**dy politicians!