I struggled with the LetsEncrypt certificate renewal using the plugin in OMV as I have a separate sites.enabled running in parallel.
To do this in the future I need to login into webmin and disable www.thenaylors.co.uk
then go into OMV and stop SSL and run only on port 80.
Then do the update of the certificates and then
rerun SSL on OMV and then re-enable www.thenaylors.co.uk on webmin.