I wouldn't worry about it Bertrand - even the British get confused by it!
Great Britain comprises England, Scotland and Wales. The United Kingdom is these three plus Northern Ireland. The Isle of Man and the Channel Islands are self-governing but are part of the British Isles ......I think......
To make it more interesting, about half of the people in Northern Ireland consider themselves Irish, and nearly half of Scotland would rather be independent of the UK. And you thought it was bad in Belgium what with some of your country being Flemish, and some of them Walloons.
Unfortunately, we consider ourselves the country that invented democracy (the modern sort, in case I upset the Greeks), and thus we feel obliged to let people have what they want, even if we know it's not the best result. Next month is the "Big Vote" - if you're lucky you get rid of nearly 70m whining Europeans who don't really consider themselves European.