But if you're recording a song for distribution in the United States, the usual practice is to license the song through a US agency, that's usually the Harry Fox Agency - and they handle the licensing for lots of Ewan MacColl songs.
Go to their songfile.com utility and do a "public search."
Then follow the instructions in their FAQ for licensing. It's about 9.1 cents per copy, in multiples of 500 - so a run of 500 CDs will cost you $45.50 per song. It's a fairly easy process to do licensing for recording. It was lots harder to get licenses to print songs in the Rise Again songbook.

-Joe-