Does anyone know the composer of this piece (link)? Can anyone suggest classical Christmas music?

I’m wondering if anyone knows if there’s a composer known for this piece here “Psallite Unigenito”: http://www.upload-mp3.com/files/112870_abyj2/Psalliteunigentio.mp3

Additionally, I’m putting together a Christmas Classical Compilation (CCC) and I was wondering if anyone had any suggestions for what I should add (it doesn’t have to be choral music). So far, I have:

Thompson – Carol of the Rose
Finzi – A Christmas Dance
The Holly and the Ivy (piano version & acapella version)
Psallite Unigenito
Gauntlet – Once in Royal David’s City
Rutter – Tomorrow Shall be My Dancing Day