Celtic fishermen are not Iberian fishermen as "Iberian" is actually a technical name for non-Celtic inhabitants of the Iberian Peninsula. Much was made of calling the people of the Peninsula at the time of the Roman conquest "Celtiberians", resulting from the intermarriage of indigenous Iberians and immigrant Celts.

We have bagpipes in North-Western Spain, too, you know?

This, of course, will do nothing to change "the scientific understanding of 'Britishness'". Where does the writer think the Celts of Spain came from? Central Europe.

Those whom the Gods wish to destroy They first make mad. — Euripides