The University of Cambridge is one of the world's oldest universities, and the hymns performed by the choir of King's College have become world-renowned for their magic. If you want the fully traditional, classic hymns to relax with, this video of "Hark! The Herald Angels Sing" for you....
can also search for more on YouTube with the following search terms: 粵語聖誕歌 (Cantonese Christmas Song) and 粵語聖誕詩歌 (Cantonese Christmas Hymns). You might need to really search through the results, as it would be a mix of Mandarin Christmas songs, hymns, even English Christmas songs...