Very impressed with Macmillan's Credo too!
The Pater and Filius sections are quite starkly instrumented, vocally almost ritualistic, with some startling leaps and high choral registers; and delicate, intimate voicings for three solo violas towards the end of Filius. The Spiritus Sanctus is more textually elaborated - I felt a slight sense of anticlimax here which wasn't entirely dispelled on a second hearing - but it draws the musical threads together tightly for a fulfilling end.
The three choruses soared impressively and expressively around the sympathetic space, the winds and brass seeming to comment on their intense declamations.
It's a striking piece - do catch up with it if you missed it live.