I have reformatted and re-installed Windows, all driver updates, Steam and DayZ on the second computer (the Windows 10 machine)
It remembers my favourites
It will not let me connect to the specific server
Additionally
I have disconnected BEC from the server
I have restarted the server
It's like there's a triple lock and details jept on the account
Additionally. It seems that once the Windows machine has been locked out by a Users account, any other steam instances on that machine (and seperately licenced DayZ instances) will not connect to the locked out server