Man of Honour
You have to turn HDR on in Windows first, then load the game and the HDR option is able to be turned on. You can then click Image Calibration and you now get HDR orientated options for brightness etc.How have you managed to get HDR working on the Ultrawide? It's greyed out for me and I can only do windowed fullscreen rather than true fullscreen.
Have managed to stop it from tripping the PSU now by limiting power to 90% so thanks for whomever suggested that one. I did order the 1000w Asus Loki PSU but its almost £300 so might send it back if it remains stable at this lower power limit.