Ok I have 2x TP Ling Powerline adaptors to extend wifi to an area of the house the main Broadband router doesnt reach.

But very recently, after new residents moved in to the flat above we have had

A device on your Wi-Fi is casting
BBC iPlayer

We do not watch TV, or BBC TV or streaing services, and we actually dont own any devices we can cast to. Its a feature we never use especially for the above.

Looking in to it further I checked our tpPLC app and reset the passwords to our TP links along with the admin login details and reset our router SSID and password too along with

its admin login.

After the above I check the on both TP Links I own 

Status->power line network->powerline device list

I can see my 2 TP links the one I am checking the status for (which shows as local device) and my other,

But I also see 2 others, bearing in mind I own only 2.

Further to that test I have installed Fing and I can see a BT hub connected to my TP link

I have installed speed test, conntect to my TP link and have brought up speed test and it shows BT as the provider. I am with Sky.

My PC is fine as it has no wifi so still shows Sky, but one of my TP links is connected via ethernet to the Sky router we have.

My concern is that I should not be seeing 2 more surely, does this imply that my mains circuit is linked to possibly one of the other flats around me?