Go raibh mile maith agat, a Mharion! Diolch yn fawr! I'm inclined to believe that the great man was from Wales, maybe from Ynys Môn (Anglesey). 'Pob lwc Cymru' today against France! Some say St Patrick was from there, so which country is he praying for?!
Well he was a Celt!, both places, Brittany in France and the Strathclyde area of Scotland were home to Welsh people at the time so whichever modern country his birthplace is now in he was from the group we now call Welsh. :)
Thanks for the information about Strathclyde. I know that Dumbarton is one of the places suggested as his birth-place but I didn't know that the people there at the time were what we now call Welsh.