What happens when you unplug the grey DSL cable at the hub?
This is totally weird.
Can you post a screenshot of the hub stats
Advanced settings> Technical log > Information
Start again. Unplug everything. Remove the powerline adaptor and remove the Ethernet cable from the BTHub. Plug the BTHub' power plug directly into an electrical socket . Make sure you have the cable from the phone socket plugged into the phone socket and the BTHub.
Power on the BTHub. What happens?
You should have a wireless signal.
If you have a device that needs an Ethernet connection plug the Ethernet cable into the BTHub and the other end into the device.