May Bradley's mother was Mrs.Esther Smith, who was indeed collected by RVW (and Ella Mary Leather) and published (4 songs)in "Traditional Carols from Herefordshire (1920). This is according to the sleeve notes on a cassette, "The Leaves Of Life", published by the RVW Memorial Library in 1989. The cassette is of field recordings by Fred Hamer and includes five tracks by May Bradley.
I've no idea if this cassette is still available of if it has been re-issued on CD. I suggest you contact Malcolm at C.Sharp House.