Well, some promising news ..
Ran the test unit today in the aircraft, using the bridge from the Classic, and apart from the odd wifi drop out (reconnected once, and rebooted the PAW once) its pretty much worked as advertised,
Looks like it may be hardware other than the bridge (or possibly software..)
I have Daves address to return the Classic for investigation, which I'll do this week now I've run the test on the bridge ..