Let me throw some additional information into this thread, in my capacity as compiler and keeper of the more-or-less-definitive Ewan MacColl Discography.

Over the years, Ewan made four completely different multi-LP sets of Child Ballads. He included additional ballads on many of his other records.

The four series were:

English and Scots Popular Ballads (4 two-LP sets, plus and LP of "Ballads Not Included in the Child Colection" Riverside RLP 12-621/22 - 12-629; later reissued as 9 individual Washington LPs, WLP 715 - 723) with A.L. Lloyd

The English and Scots Popular Ballads, Volumes 1 through 3 (3 LPs, Folkways FG 3509 - 3511)

The Long Harvest (10 LPs, Argo DA 66-75) with Peggy Seeger

Blood and Roses (5 LPs, Blackthorne ESB 79 - 83) with Peggy Seeger

So that's 26 LPs, not including the "Ballads Not Included" one. I haven't compiled individual lists of tracks on each record, so I don't know exactly how much overlap occurs from one series to the next. At a guess, there are maybe a hundred different ballads included (not counting variants).

The Folkways titles are still in print, available on CD or cassette from Smithsonian Folkways.

Riverside now belongs to Fantasy Records, who were not at all interested when I asked them about licensing the ballad series for re-issue. They have their own very successful re-issue program for many of the great old jazz and blues LPs in their catalog (they also own Prestige and several other labels), so they have a blanket policy of not licensing things to other labels.

I'm not sure about Mudcat's policy on outside links, so I won't include the URL, but the discography is online and easy to find through your favorite search engine.