Thank you for the tip! I'll try that.
Edit - no actually - I will not try that, since I'm not prepared to lose my installed applications and other customisations. This is just re-install essentially. I don't keep my data on the C drive anyway, so if I wanted to re-install I would already have done that. I am aware that pretty much all issues can be solved with a re-install.
I also ran the Windows Start Menu trouble shooting tool which I just discovered.
It finds one issue -
I'm going to look into that as well. It's surprising to see this result, since this is a fresh upgrade AND I have just ran DISM and SFC scannow. So one check says everything is fine and the other, above, says there's a problem
||Required applications are not installed correctly.
|| Not fixed
| "Microsoft.Windows.ShellExperienceHost" and "Microsoft.Windows.Cortana" applications need to be installed correctly.
C:\WINDOWS\system32>Dism /Online /Cleanup-Image /RestoreHealth /Source:wim:N:\sources\install.wim:1 /limitaccess
Deployment Image Servicing and Management tool
Image Version: 10.0.10586.0
The restore operation completed successfully.
The operation completed successfully.
Beginning system scan. This process will take some time.
Beginning verification phase of system scan.
Verification 100% complete.
Windows Resource Protection did not find any integrity violations.