OK, so here is hopefully the end of the saga with my findings - wifi interference!!!
Brief recap. I bought a PAW Classic recently, planning to use in my aircraft using my cigar socket/USB adapter, and an Apple 10W charger at home for test and set up. However trying to set up at home I couldn't connect to the PAW wifi using my iPad Mini, iPhone, PC laptop or MacBook Pro.
However I could get the PAW to work off a similar charger my the office. Tried again at home (but with hindsight only in the same room as the wifi router!) and it wouldn't work.
New problem, the PAW works fine from my cigar lighter adapter. However on power checks when I check the engine at idle the low voltage warning light comes on and the PAW does a restart!
So I bought an Anker PowerCore 20100 for use in the air, but also tried it for home testing and found exactly the same problem, couldn't get it to connect on wifi. This is testing at my desk at home as before.
Now with the freedom to move away from power sockets I tried in a different room. Low and behold it worked perfectly!
Then came the tip about wifi interference. I use an Apple Extreme Base Station, and the 2.4 MHz band was set to Auto. Changed it to band 1. PAW now connects first time every time to any device. I have set the PAW to channel 11 to give even more spacing. When the PAW wouldn't connect I was 2-3 metres away from the router, so the interference was considerable. And now it will work at my desk powered by the Apple 10W charger too!
Thank you everyone for your help.
Now all I've got to sort out is to stop the PAW and battery sliding around in my cockpit!