What about Kittredge's Riverside 1-volume edition of Child? Was this available in the UK?

It was employed for decades in the US as a textbook in folklore classes. One of my high school teachers used it in the 40s, gave it to me in the late 50s because I was so interested in the subject, and I used it for English 371 in the 60s, which saved me $2 or $3 on textbook costs that semester. The Kittredge edition must have been in print for a good 60 years.

It's an abridged edition so it doesn't include every variant, but it's quite representative though without the entire critical apparati of the 5-volume set. I don't think it has the dozen or so melodies that the original included. (Haven't seen mine in years, as I bought the Dover 5-vol reprint in the 70s and paid something like $25 for it.) Five ballads are omitted for reasons of prudery -- "Trooper and the Maid," the dirtier of the "Beggar Man" songs, the one about the grotesque bride covered with snot, and a couple of other obscure items. Oddly enough, the well-known incest and kid sex ballads are not among the omissions. I think 4 of the left-out items are in the high 200s/low 300s.