I chanced upon this at archive.org:https://web.archive.org/web/20160129070555/http://setintosong.co.uk/indexbc02.html?page=1;
It's a defunct website about the 2008 Peter Cox book, Set Into Song: Ewan MacColl, Charles Parker, Peggy Seeger, and the Radio Ballads. Lots of interesting material to explore, including a script for "The Big Hewer":https://web.archive.org/web/2016*/http://www.setintosong.co.uk/downloads/PDF/rb_website_big_hewer.pdf
New Link from Reinhard: https://cpatrust.org.uk/set-into-song
Link to the book and Radio Ballad Transcripts.
Can we find other Radio Ballads scripts there? I haven't figured out how.
Lots of Ewan MacColl recordings here, including what appears to be full recordings of at least some of the Radio Ballads:
https://ewanmaccoll.bandcamp.com/music