...and then running the following command as administrator in the command prompt:-
After entering this and opening the Control Panel > Windows Update, it appeared I was well on the way to receiving the Windows 10 upgrade
I wondered if this error was due not meeting minimum available free storage on the C drive - I had about 12GB available on my SSD, so managed to free up another 10GB by temporary relocating a huge 10GB backup file found under the C:\Users\[MyAccount]\AppData\Roaming folder used for ITunes. - Still no luck!
I then tried another route to carry out the install - Windows 10 can be downloaded using the following tool:-
I ran the tool (MediaCreationToolx64.exe) using the upgrade route rather than burning installation media, but sadly this failed too,
I spotted that running this tool, created another hidden folder:-
In this folder was a setup file:-
Running this file gave me the upgrade option:-