Okay, this is it, out of MacBean's book:
[I hope I space it better this time]

1. Child in the manger! Infant of Mary;
Outcast and stranger, Lord of all!
Child who inherits All our transgressions,
All our demerits On him fall!

2. Monarchs have tender Delicate children,
Nourished in splendour, Proud and Gay;
Death soon shall banish Honour and beauty,
Pleasure shall vanish, Forms decay.

3. But the most holy Child of Salvation,
Gentle and lowly Lived below;
Now as our glorious Mighty Redeemer,
See Him victorious O'er each foe.

4. Prophets foretold Him -- Infant of wonder;
Angels behold him On His throne;
Worthy our Saviour Of all their praises,
Happy for ever Are His own.

----

It's just the sort of thing that could have been in the great Oxford Book of Carols (1928, I think), but of course antedates that.