It doesn't matter about the firmware difference of the 7020P kits as they are working properly. As for the 9020P kit, you can try to turn off its idel mode and power save mode with the latest tpPLC...

When PC lose connection, how about the LED lights on all the 4 units, if they are still paired up( with the 2nd LEDs lit)? If the Unit1 is working normally wiyh all 3 lights lit up and getting...

It's weird. You can contact tplink support to get some advice.

VR900 does not support Annex B. Confirm with BT it's annex B or not before you replace or return the router. I don't know BT UK has annex b

Better do not connect any devices to the tplink router first, including your talk talk router. then connect your phone to the tplink WiFi network and login the tplink router. You can also try reboot...

Whether it supports monitor mode or not depends on the adater chip set, which is RTL8188EUS-VG-CG. You can surf the internet to figure it out