When I lived in South Africa, one of my best friends was named Paul (in fact his name, like so many Welsh males, continues to be Paul). I know from experience (dude) that you do not want to make the mistake of accusing the Scots, or Welsh, of being “English.” It’s like calling southerners “Yanks” (which happened to me a lot in South Africa, incidentally). OK, enough biographical nonsense. Enjoy this highly educational video about what constitutes Britain, the British Isles, the United Kingdom, etc.
Update: I forgot to mention that I think I saw this first at Challies.