I am Swiss so I am not concerned although I have a deep interest for the Celtic culture, especially of the ancient Celts. I understand the animosity against the English people, I am not really fond of their culture, history and attitude in general. But on this matter, I don't follow this logic about the British Isles being a terminology imposed by the English imperialism upon the Irish people. There are evidences in Polybius, Pliny the Elder and Pseudo-Aristotle works showing that the ancient authors viewed all the Islands as being a part of the British Islands, including Ireland.
I disagree. First of all because I know the archaeological evidences for Ireland's early Iron Age, they are not abundant. And the heroes you are mentionning are only known from tales and myths. It is impossible to date accurately the events occuring in the Gaelic tales.