Always uplifting to hear a church organ in full cry. Should be great at St Mary's. Only last week at the Cathedral in Boulogne, I'm showing off now, I heard JSBach's Toccata and Fugue wafting through the powerful organ pipes. The piece of music is indeed powerful and very often a standard organ piece. You might hear it at St Mary's.
Good luck to St Mary's with the event.
Speaking of Boulogne...here is a picture taken from the inside of the Dome of the Cathedral there ( Notre Dame). The outside will be familiar to many, in fact on a clear day I can see it from my rear window, but here to balance things up is a shot of the inner for all to enjoy. Huge it is...