No, They will not fit. As Andy says above, GTI is 55mm strut. SDI is 50mm strut.
Oh and JOMs are turd
Have you ever run JOMs?
FYI, all the JOMs are 50mm and they come with an adapter bracket, as pictured at the top
I have JOMs and have had since December 2011, and they are not the best but - I'm sure you can find better - But in conjunction with my ARBs they do sharpen the handling and the car is almost dead flat through corners. On a track they would perhaps be a little soft but on the road they are completely acceptable.
For the money (as in, £180 brand new with a 2 year warranty) you simply
can't do better.
All the GTIs are 55mm strut. Basically if your calipers say FS III on them then you have 50mm hubs (these are only on the 280mm disc cars, smaller engined vehicles such as the 1.4, 1.6 and 1.9 TDI. But this is not a hard and fast rule. The only way to verify is, as I said to check your brakes.
If your carriers are INTEGRATED into the hub (as in, non removable) then you have 50mm hubs.