Well, to be fair, at that time there was no real contention between the Roman and Celtic churches, and I have not seen any evidence that they considered each ot

Well, to be fair, at that time there was no real contention between the Roman and Celtic churches, and I have not seen any evidence that they considered each other outside of one another's communions. The idea of "Roman" Christianity had not taken hold until Gregory the Great, and especially his successor, Sabinius, who formally accepted the supremacy over all the bishops. The conflict between the Celtic and Roman churches came later under Augustine of Canterbury, who required the Celtic churches to adopt the Roman rite, abandon their old Italic Bible translations, and adopt the Vulgate. That stirred up quite a kerfuffle.