Good news and bad - and ultimately good triumphs!
Good news, - with the virtual box ethernet adaptor disabled under its Driver tab, ipconfig and Synergy on the server both agree that the ip associated with the VB has disappeared and the 'regular' ip for the server is now bolded on the Servers synergy window.
Bad news is that setting the client to the servers Synergy window's bolded / regular ip still did not produce a connection.
The good news is that this was because the client had connected to a different local wifi LAN - setting this onto the same LAN as the server (VB a