I have answered my own query.
I set the port number to 1 so that when logging in the web browser is picking it up (I assume). A bit of a blag but it's working fine and secure.
i.e. I've set my IP address for hosting as 000.000.000.000:1
This logs in off and on site without issues and without needing to change to suit either access points. Again this is no replacement for buying the required number of licences and it has practically none of the functionality of the full appliacation but it gets clients off of our backs.
I hope this helps anyone else who's had this trouble.