I remember a dj, possibly JW mocking them on air, about the breakthrough and occasions when the signal would seem to trip out for a second. He said that they, Radio London, needed a part that Caroline had and they didn't, but I can't remember what. Aerial part?
I had a theory of my own: that they were trying to find a frequency where they could use more bandwidth, but they would have heard that awful whistle and decided to ignore it.
I have no technical knowledge and may be talking rubbish.