Do you know anybody that is a BT broadband customer who would be able to try and connect to the BTWifi signal to see if it does actually work because I agree with licquorice that although it may be transmitting the SSid it won't actually be connecting to the BT network so would not be able to allow any body to access the Internet.
However having said that I would say there should be a way to turn it off if the customer does not want it transmitting.
No need to pay, just see what IP address your device gets when connected to the bt wifi SSID.
Through my network/whole home it’s 192.168.0.93
I don’t know through BT Hub but can pay for another hour and see, if you think that would be helpful?
Are you using a BT Homehub aswell as the disks?
Is it possible that the disks could be repeating a BT Wifi signal from another nearby home hub?