I note that the MacMillan Ecce Sacerdos Magnus was programmed for the Bishop Comensoli enthronement but apparently not sung. It is a lovely piece, sung at the enthronement of Archbishop Fisher recently in Sydney, and was originally commissioned for the ordination of Bishop Gilbert, the current bishop of Aberdeen, Scotland. Westminster Cathedral Choir have recorded the work.
One of my favourite settings of Ecce Sacerdos Magnus is by Anton Bruckner. Here Westminster Cathedral Choir sing the piece after the Papal Mass at Westminster Cathedral in 2010. I have deliberately started the video a few moments before the piece begins, to serve as a reminder of what remarkable affection young people showed towards Pope Benedict, an affection clearly reciprocated by the Holy Father (as he then was). Your patience will then be rewarded by a stunning account of the Bruckner motet.