We appreciate the OPs desire to try and learn about our culture by before beginning a mission as a British spy operating undercover as a British diplomat.

Maybe OP can clarify some terms for us Washingtonians (yes we call ourselves this even though it conflicts with the previous usage that we never say we are from Washington) these three come to mind, one is the name of the island I know but the other two? Political terms for countries that are both separate and together?

United Kingdom England Great British