The Republic of Ireland (Eire) is NOT part of the United Kingdom - they're part of The British Isles though.
Here's how it works:
Great Britain = England, Scotland and Wales
United Kingdom = England, Scotland, Wales and Northern Ireland
British Isles = England, Scotland, Wales, Northern Ireland and Ireland
Saying he could be the first champion from The British Isles would be technically correct - but why not just say Ireland?
The problems with Ireland and Northern Ireland cause a lot of friction - hence the UK part hitting a nerve with the Irish.