How do you start Arducopter? Your RPi/Navio and your Laptop usually get another IP address than in your home network. Most Android phones use 192.168.42.x. You have to modify your telemetry options or use two, one for your home and one for your phone network. You could also use tcp instead of udp and have Arducopter listen on any adapter for incoming mavlink connections: -A tcp:0.0.0.0:6000 for example.
You can use any port, the zeros are important.
My man Seb!! Thanks for such a quick and thorough response.
I rushed to my PC at 8 am this morning and managed to get it working with my phone thanks to your response.
I usually fix the IP of the GCS when I am on my home network. However when testing via my phone as a hotspot I was using my home network IP address that I usually fix to and it did not like this. Furthermore, I hadn’t told arduplane to broadcast a third telemetry option (bit of stupidity for me there!) so no wonder it wasn’t working.
I like the idea of a using a second pi 3 as a hotspot though to take my phone out of the equation all together.
Cheers for the help!
After much trial and error, I could not get the raspberry pi 3 to work as a hotspot. If anyone comes across a good definitive guide on how to do this, I would be keen to know.