Can this thread be closed.
Shortly after posting my question my PC suffered a catastrophic BSOD, caused by a problem between the Corsair ICUE software/firmware and/or a recent windows update.
As it was impossible to get into safe mode or repair the system partition on my samsung NVME SSD (Issues with MBR vs GPT), I decided to just do a clean install.
Starting with a fresh install onto GPT, and doing all the windows updates has solved the problem of the security rollups failing. It did take me while to find out why the keyboard software/firmware was still causing windows to crash, but I have now solved that also.
Thanks for looking.
