On the matter of the A, it could well be an Alpha, but I stupidly discounted that possibility, there being no Omega... but of course some panels are missing, and indeed there is no reason to assume that the current order is the original one.  There is an alpha-and-omega on a pew-end, but I do not have a picture by me, and having a useless visual memory cannot summon it up for comparison.  I will check next week, when I hope to be able to nip over again to the church.