After a number of
VIDEO_TDR_FAILURE blue screens I went back to HP and this time they replaced the motherboard in the the laptop. The repair report specified bad GPU memory as the fault.
So far both the throttling issues and blue screens from the previous 2 posts (1 / 2) have not been seen. HP were fast to get the repair completed. If I have issues with any machine in the future I will be more proactive in contacting the manufacturer rather than trying to work around myself with drivers/updates etc.