OK. I'll break down and give you the main source, revealed in the email from Wellesley's indefatigable music librarian, Pamela Bristah:

"It is in an anthology, 'The English Carol Book,' edited by Martin Shaw and Percy Dearmer (London: Mowbray, 1921)... It is titled, 'The World is Old,' the composer is Joseph Moorat, and the words are by Lawrence Housman."

She'll send a copy of the song when she receives the anthology on interlibrary loan.

TA-DA!!! Thanks to all of you, Jean