Well, Im pleased to report that I used Nox on a W10 machine (running android 7 and using the settings as previously outlined) to successfully run the firmware update tool.
I have since updated the firmware to 1.5.3.3 and have maintained connectivity since (I had to re-boot the router for it to pick the weather station up again). So, fingers crossed, everything is now back on track.
Ill report back if anything changes.
Thanks to those who provided assistance (including the developer who was excellent).