I have a slightly different problem. With only 3 Ethernet connections on the back of the Hub and I need 4, (I use a heating Hub, a Phillips Lighting Hub) plus I have a poor WiFi coverage due to aspects of my building, so I cannot get a 4G signal from my EE Hybrid Connect. I have communicated many times with BT, so , like several other members, when my contract expires I shall move. My Broadband signal is better now, but when it drops I have no backup.
Are you on FTTH @MajJim ?
If not (i.e. you are not connecting your hub to a ONT), you can turn the 4th port from a WAN port to a standard port in the hub settings.
Just add an Ethernet switch to one of the Ethernet connections on the home hub. That will give you four extra ports.
Like this https://www.tp-link.com/uk/business-networking/unmanaged-switch/tl-sg105/v6/
Thank you for all the helpful suggestions. I will follow up on them. It is a shame that all my communications with BT help did not suggest these options. I was considering setting up a Mesh Network but in the meantime I will try what was suggested. Thanks.