Finally got some where last night, managed to reboot the PC a combined total of 40 times without a single BSOD. Previous to this i'd be lucky to get 5.
I had to increase the bios vcore to 1.4000v with LLC on.
This is giving me idle voltages of around 1.382, and 1.39 load. Both checked with CPU-Z.
On face value it seems i got a below average E0 Q9550. Even setting 1.39350 in BIOS leads to the odd 124 BSOD . Never seen a E0 Q9550 need so much vcore for such a light oc.
I will continue to test, as maybe i just got lucky. But it does seem far more reliable with this high vcore.
This also answers why the PC was blue screening at idle but not under load. While underload LLC was pumping it with more voltage, something it obviously needed. When not underload and with a lower voltage, it was not stable.
Not sure at the moment if it's worth running at 3.84ghz with such a high vcore, or scaling it back down to a lower level where i can significantly reduce the voltage.
CPU is under water cooling, temps never exceeded 55 degrees C in IBT.
Everything else is good however, 1.28vtt, 1.56 PLL.