"My first reaction when hearing/reading any reference to "Southern Ireland" is to think of the Waterford/Cork/Kerry area, not the whole country."

I agree. Just as when people say "Ireland" I think of the island as a whole, as a geographic entity, not a geopolitical one.

People really should be using the word "Republic" by now, because it is accurate, not because of any political ax I have to grind. If I had a political ax to grind, I'd refer to the south as...

Let's just be thankful I've no ax to grind, eh?

I just get tired of people, especially the British people who live right bloody next door, not knowing what the hell to call Ireland, north and south. I mean, it isn't like they haven't had proper lead time to learn to say "Northern Ireland" and "Republic" or "Republic of Ireland" now is it? Over half a century later, and they still can't sort it out? I don't think so.