"...led it is claimed by Joseph o Arimathea?"

So much of Joseph of Arimathea's "British whereabouts" or "mission" are legendary, Eliza lyons. If true, I am sure Anglicans by now would have created an archbishop of Glastonbury (which abbey Joseph was to have "founded") instead of an archbishop of (Rome-founded) Canterbury. But even Anglicans don't take the legend, fable (Arthurian or otherwise) seriously, preferring Pope Gregory's foundation over which Anglican make-up can be applied.