In an Irish documentary series some years ago, it was postulated that Coptic Christianity was brought to Ireland by traders along the Atlantic coast, and that it was therefore easy for the organised Catholic system to displace the original, non-hierarcical system.
As part of their research, as well as comparing Irish caligraphy and patterns with north-african ones, they took a gaelic singer to a north-african marketplace to perform un-announced and then interviewed locals about the performance. the concensus was that the singer must be from another area because they didn't understand the dialect, but that the music was local.
C.H.