OK so, I just went 8 days straight with no crashes. Played a rediculous amount of star citizen.
Anyway, it started crashing again today.
It was the first day it's been above 18 degrees Celsius outside.. as my pc usually lives in the attic, add a few more degrees for trapped heat, I'm suspecting these cpu's (or something in the pc) is fragile when it comes to a bit of warmth.
Took my pc back downstairs where its a bit cooler, and is working fine again.