Earlier in this thread I stated only England, although it has just occurred to me that I have already represented England, Great Britain and Hong Kong in various International Sailing events.
Personally, England, England, England and England.
But both my daughters would qualify for Scotland via a maternal grandmother, and my granddaughter would qualify for wales, because she was born there. I don't expect it to be an issue anytime soon, though, because she is only one year old (last month)
England - birth, both parents, all but one grand-parent
Scotland - my grandad
Republic of Ireland - my gran once drank some Guinness. probably. It worked for Tony Cascarino/Andy Townsend so I reckon it's worth a shout.
Edit - bit late on the Guinness gag, I see. It's not been my afternoon really.