At the risk of jinxing myself. I think I have solved this issue. Following the suggestion on another thread I downloaded and installed drivers 314.22 for my GTX 280. This immediately stopped my crashing, I did it yesterday and have no had a single crash since.
In fact, I tested the hell outta it today, I loaded up FFXIV when I loaded my PC this morning, 13 hours later and I have finally closed it (I was not playing all this time, I just left it running while I went about my business, but previously, it would have crashed when doing nothing). 13 Hours without a crash?
I haven't had that since launch, try it guys, it might work for you.
/edit - I also have my frame rate limited to 30 fps, having it limited to 30/60 too might be important some ppl said on the other thread.