They compete as team GB, further demonstrating the madness of trying to define a nation

Team GB is a trademarked brand name for the United Kingdom olympic team. (I think because "GBR" is the established letter code used so GB has some brand recognition factor in an olympic context.) It's controversial since "GB" can be seen to exclude NI although the team includes the whole UK.

It's even more than UK. Includes different Crown Dependencies like Isle of Man, British Ovsersea territories like Montserrat or Gibraltar. https://en.m.wikipedia.org/wiki/British_Olympic_Association

With the British it's always complicated :)