Ah, I assumed that when you said "Are you able to see aircraft using the V6 software instead of the web?" I thought you were about to reveal the secret of what I needed to do to correct the situation. Meanwhile, I have tried using different computers to no effect - but as I now realise there is indeed a problem at t'other end.............just received a reply from ANRB Support "Apologies we are aware of this issue and its being worked on.
Regards, Alex Johnson
AirNav RadarBox Support"
So I shall go and do something more festive whilst I await the fix :-)