I had a look around the xda forums but no luck, suppose i'll just have to roll back to stock rom.
Is there any way of finding out what stock ROM to install for my model - Obviously forgot to note my original before I installed soulgem!!
SN A novo7crystal121008G06667
Yes there is a compatibility thread for determining your batch number and which ROM's work for it. You have the same batch as me so you would need the 0928 stock firmware.
So are you saying that this app you want to run works on the stock firmware? If it does, you might just need to edit your build.prop to the right region to get the app functional again. You can use https://play.google.com/store/apps/details?id=org.nathan.jf.build.prop.editor to look at and edit your build prop but I'm not sure exactly what you would need to change because I'm not in your region and don't have that app. There is a bunch of info in the build.prop on your region though, so it would be worth a shot.