Easy defence - fuzzying
If they only listen to ones wifi, and assuming the wifi is strongly encrypted, the defence a home would have against the BBC is to add random traffic to the wifi - so called fuzzing. I guess this could become an opensource project - imagine Raspberry PI in Wifi simply generating traffic to a website on the Internet. Very hard to distinguish on the Wifi.
That is why I am puzzled why the BBC bothers with Wifi when they could (using RIPA) tap to the ISPs directly. And by extension of that, why not just correlate IP addresses of iPlayer users with paying households.