I had genuine grilles on a replica (Xparts) bumper, fit ok. I eventually got a genuine bumper in replacement. As above, GT facelift and GTI skeletons are the same - all grilles are swappable between them. As are the Jetta centre grilles.
R32 is different altogether.
The difference with your fogs is that the light unit has different mounts between the bumpers. I got a GT/GTI/Jetta set of fogs from China, split them & my originals and swapped them over, that way the mounts all lined up, glass was angled correctly for the grille and plug fitted the loom still.
With the likes of Xparts, their fog grilles are 'GTI look' but standard fitment designed to take your original lights.
Like I have said to everyone doing this, please buy genuine. A replica will never make you 100% happy.