jimmyt, "Celtic" is generally taken to mean "of those who speak the p-Celtic and q-Celtic languages" (or "spoke") - in other words, Irish, Scots, Welsh, Cornish, Manx or Breton; the Basques speak an ancient language not apparently related to these, but are included in the definition by those who use it as a flag of convenience.

Some Irish songs are related to English traditional music; for instance a lot of music from Wexford, where many Englich craftworkers settled, sounds English - like "Come to the Bower".

Irish and Scots music are fashionable at the moment; in the 1950s English folk music was the thing. These trends come and go, and enrich other traditions as they move.

If there's going to be a quarrel about this, count me out. I'd sooner fight about something more important.