Out of interest, what Freeview box do you have? I was under the impression that most freeview boxes just loop through the RF signal to your TV and that they don't actually "transmit" an RF signal to your TV. The freeview picture is normally transmitted via Scart, and even then probably via composite. Some higher end models may have RGB on Scart, but I'd be interested to learn if any models actually output a RF signal.
Plan B for me was to hook the Freeview via Scart (composite) to my Video Recorder, and then turn the video to AV1 and then watch the "video" RF signal which is put to the RF distribution system.