That's the book I was thinking of. It even includes scripts!!
Of course Ewan MacColl only used the Radio Ballad format as a vehicle for promoting his songs, and left wing ideas about society. It was Charles Parker who was the producer and driving force.
But they were not the first. The BBC in America sponsored a number of Ballad Operas with Alan Lomax and Douglas Geoffrey Bridson, long before Maccoll and Parker were around.
Some of these Ballad Operas have survived, some have been lost.
But Lomax and Bridson were the FIRST to develop the Ballad Opera / Radio Ballad genre.