Issue in getting Port based multi-tenant working in ERPNext Docker Ubuntu

Hello. I managed to get a production single company ERPNext working quite easily in a Docker instance but am battling to convert this to a port based multi-tenant set-up.
I used the method set out in : frappe_docker/docs/port-based-multi-tenancy.md at main · frappe/frappe_docker · GitHub but I have obviously missed something because it doesn’t work and I get an “Unable to connect” response when trying to log in to any of the ports I set up.
My question relates specifically to the statement on the webpage: Change site1.local to site name to serve from bench. What does this mean when as far as I can ascertain one does not have access to bench in a Docker production environment?

I appear to be getting this sorted on my own thanks

How did you solve it?