The choir is practicing an arrangement of Michelle (Lennon/McCartney) by Grayston Ives. I believe this is the arrangement performed by the King’s Singers in the video above.

I must admit, I don’t like this performance as much as I expected to. As one of the commenters on YouTube says, “They are undoubtedly brilliant singers but they could perhaps do with a little less enunciation and a bit more rhythmic freedom.” Quite. Let’s see what Capital Choir can do. In connection with that, the arrangement at bar 51 is marked slightly slower than tempo. We should be able to manage that!