Vaughan Williams wrote an essay on a related subject (Info from HERE:

Vaughan Williams, Ralph. "The Influence of Folk-song on the Music of the Church." In National Music and Other Essays, ed. Michael Kennedy, 74-82. 2nd ed. London and New York: Oxford University Press, 1987.
The history of church music includes many borrowed folk tunes and contrafactions, from the Tonus peregrinus (foreign tune) of the Roman church to the use of popular tunes as hymns or chorales well past the Reformation.
Works: Tonus peregrinus (Gregorian chant) (76); Valet will ich dir geben (German chorale); O Filii et Filiae (Sequence) (77); Thomas Oliver: Helmsley (hymn tune) (77); Louis Bourgeois: Old Hundredth (hymn tune) (77), Old 113th (hymn tune). (RCL)

A number of English examples based on folk tunes can be obtained from The English Hymnal (Oxford, 1906, 1933; music editor was Vaughan Williams; see "English Traditional Melody" in "Index of Composers and Sources").

~Masato