Can anyone give me some advice on which I should get? Only going to use for simple recordings and I will only record one guitar so no need for the mic inputs etc that the UX2 has.

But can anyone tell me if the UX2 has any great advantages over the GX other than more inputs etc? They both come with the same software so is there any need for me to get the UX2 at a greater price?

Thanks in advance
I've owned both. Other than the inputs they do the same thing. If you don't care for the mic inputs that's cool, but consider compatibility with studio monitors because wearing headphones can get annoying after a little while, especially when playing heavy guitars. I believe even the UX1 can be used with monitors as well, which should be a bit cheaper. That is if you have or ever plan on getting a pair of studio monitors anyway.
If you are not interested in using their emulation software (Line6) I'd suggest looking at a different brand, Roland, Cubase, PreSonus, Focusrite, etc.
If you're ok spending a little more for quality, try Audient iD4 or iD14.