Hi Toufiq, thanks for your ogoing help, it very much appreciated - I have spent the day figuring out what the developer must have done when the site was set up some years ago.
After a lot of rooting around and loading/unloading I believe they created an "above" and "below" position using:
https://archive.joomshaper.com/forums/module-position-before-and-after-component
Instead of putting the file where the above linked instructions (link above) say - they infact altered "componentarea.php" directly. Probably because the directory recommended in the instructions does not exist in my sites template structure. As per the write up in the link the "above" position exists but it cannot be seen in Helix as there is no XML change.
This is where my problem came I think, because when I tried to upgrade Helix, or the Template, or the newer pagebuilder I believe this file "componentarea.php" was overwritten causing the hidden (but existing) "above" and "below" positions to be overwritten and therefore non-existent . Hence my disappearing modules assigned to the "above" position.
At this stage I am thinking to do the upgrade again and then replace the new "componentarea.php" with my existing one - but that would mean I would have to do this each time I do an upgrade - any suggestions?
Thanks!!