Radio 4's Feedback programme covers topics to do with all the BBC's radio channels. In recent series, they've spent quite a bit of time on the proposed cuts to local radio. They would be the obvious place to cover this, but they're off air at the moment, back in October. Worth sending in comments now, though, as they must be gearing up for the new series.
I'm not up to speed on this issue, so hazy about who Roisin Murphy is or what she does or has said. If there could possibly be a statistics-related spin on it, another possibility is to contact More or Less, which is currently on Radio 4 in the same slot as Feedback gets (they take turns). Their remit is to take listener queries and factcheck them.
Will be interesting to see if the BBC covers this as a news story. That would probably flush out the 6 Music Controller or similar.