Found a possible solution, if you're on Nvidia. while messing about with EVGA Precision, due to the fact that event viewer was showing a shedload of nvidia driver crashes whenever the game crashed (no visible error messages however)
1) I found that SWBF2 was running with GPU clocks that were WAAAAAY above what my card can run stable at... not sure why it does this but it does, seems like its overboosting the card as I noticed peak core clocks of over 1300Mhz before it crashed... which my card simply can't handle on air cooling and stock voltage
2) Normally my 780Ti GHz Edition can boost to a stable 1250Mhz on the core and 7Ghz on the VRAM, which is basically the card as it came out the box.
3) To seemingly SOLVE this issue with SWBF2, had to run my card as follows: -50MHz Core and -300MHz Memory. with power set to 100% and Temp set to 86 Centigrade.
4) This then showed the in-game core clock as: 1228Mhz, with 6.4Ghz VRAM. Runs happily on ultra no FPS drops and so far no crashes.
Hope this works for any other Nvidia users, because rolling back drivers doesn't work, that's an AMD only fix - trust me i tried.