It's been long enough for me to state, but I used to work for a contractor hired by CMA Communications.

ISPs of this size try and maximise as much profit out of their customers and being that a lot of CMA's sites were over provisioned and are barely able to provide telephony service without incompetence-y along the way, it is not shocking that ads being injected into pages is a new thing for them.

To see these bullshit ads showing up on random pages is far from surprising.