The Three Great Enchantments of the Island of Britain:
Of Math ap Mathonwy, he was a mythical king of Gwynedd, who had a magic wand and created the woman Bloddeuwedd out of flowers, with the help of his nephew Gwydion. His story, recounted in the Mabinogion, is found in "Math fab Mathonwy."
Of Uther Pendragon, we know he was able to shapeshift--with Merlin's help--into the form of Gorlois, and concieve Arthur upon the unaware Igraine. This tale is not a French invention, for it is from Geoffrey of Monmouth that we first hear it. Menw is mentioned among Arthur's retinue as an enchanter; though I can't think of one particular decendant in French Romance, his role may have been taken over by Merlin (Myrddin).
Coll son of Collfrewy was keeper of the sow Hen Wen, who gave birth to the Cath Palug on Môn. Yes, this is where Lloyd Alexander got the character of the same name and story in The Chronicles of Prydain; in the triads, though, we see that he has the powers of an enchanter, and it has been theorized that "swineherd" or "pig-keeper" was code for magician or druid, inasmuch that the pig was considered a divine animal, brought up from the underworld by Pwyll, father of Pryderi.
Back to the Welsh Triads.