Further to my earlier posts I believe I have resolved my issue with the start menus - to do so I did the following:
1. Completely reinstalled Windows 10 again from scratch, and
2. Having identified that my ESD Windows 10 USB Installation Drive had no install.wim file (but did have install.esd), I changed the appropriate line in the relocate.xml file as follows:
Whether simply reinstalling fixed it or not, or whether the above code change did I don't know...
<cpi:offlineImage cpi:source="esd:E:\sources\install.esd#Windows 10 Pro" xmlns:cpi="urn:schemas-microsoft-com:cpi" />
It has again created the odd defaultuser0 user directory sometime after I initially logged in the first time, that is missing items that are in the 'Default' user directory... But I now have 4 operational user logons all with functional windows start menus, so happy for now...
...and thanks again Kari for the original tutorial.