My profound apologies go to St Trillo.
I assumed, due to the Saxon styling of the chapel in Rhos, that he must have been Saxon.
But no! According to the internet extract (below), he actually was a Breton (from Brittany) who may have fled from the Saxons.
I wrongly assumed that because he was too late to be Roman, too early to be Norman, he must be Celt or Saxon.
I ruled out Celt because he was a missionary, and they were a bit too hostile for that in the 6th Century.
1. St Trillo,
Where did he live?
From the early 3rd century, the Bretons fled both the problems of the land as well as the invasions of the Saxons. They left the British Isles to settle in Armorica and gave her her name - BRITTANY. Progressively the Breton language took over from the vernacular Latin.