Ahh, so progress.
I now get (on production - leaving the UUID as it was)
root@4cfc0a0:/usr/src/app# export DBUS_SYSTEM_BUS_ADDRESS=unix:path=/host/run/dbus/system_bus_socket
root@4cfc0a0:/usr/src/app# python activate_connection.py resin-hotspot
No suitable and available 802-11-wireless device found
Which is exactly where the trail goes cold on the original forum thread - Raspberry-Pi Wifi Access-point
Hopefully my nmcli outputs will help identify the issue.