Excused my stupidity as I don’t know an awful lot of docker.
To use the monitor_docker add-on for HA, I must bind the volme var/run/docker.sock into the container to see the sensors.
(EDIT - If you do not know how to do bind the volume so you can use monitor_docker, see my comments in post 10)
However, once I then update HA, this is removed from the docker rebuild and I need to re-bind the volume before the monitor_docker sensors reappear.
Is there something I can do to prevent this?