Thanks Chris.
All sorted now – was no fault of your plugin.
FYI I am able to restrict access/visibility to signed in users with certain permissions via this handy plugin: https://wordpress.org/plugins/user-specific-content/
Page code therefore:
[O_U user_role=”otheruser,administrator”]
[bex_folder]
[/O_U]
The two work well together, and they suits my use case for now.
In future I can imagine I’ll need multiple Blighty Explorers / root folders; and via the user plugin I can give different user roles different folders.
Thanks again for the help!