OMG I have had to waste four hours on this crap (you see why I mostly use Linux) so having gone to through the steps on the previous link over the error code 0x80073701 having enabled the appropriate four startup services
net start wuauserv (already running)
net start bits
net start msiserver (started it up but for some reason I cant change it to automatic in services.msc)
net start usosvc (already running)
which did not resolve the problem, I then run
DISM.exe /Online /Cleanup-image /Restorehealth
and then DISM.exe /Online /Cleanup-image /Restorehealth
using the original windows 10 204 x64 iso mounted and reinstalled image files for that
Still success, I eventually came across an article saying I needed a security update installed,
KB5005260: Servicing stack update for Windows 10, version 2004, 20H2, and 21H1: August 10, 2021
None of these 21H1 for x64 would install and they said they were wrong for my system (I tried the to 64 and 86 out of curiosity)
I then read another article saying if the above wasn't working I'd need the following instead:
KB5004313: Setup Dynamic Update for Windows 10, version 2004, 20H2, and 21H1: July 20, 2021
That was downloaded as a cab file and after extraction I got yet another error message saying it wasn't right for my system.
Absolute nightmare.
Would the Reset my pc fix all this? Its annoying I'm going to have to prat about installing various softwares again.