I'd go with Land Of Hope and Glory if I was British, with God Save The Queen reserved for England itself.
The other way round would be more logical, since she is Queen of the whole UK, while the Scots in particular played as big a role in running the British Empire as did the English.
Incidentally, if we're going for Edward Elgar, there's also "Song of Liberty" set to his
Fourth Pomp and Circumstance March. It's chorus includes a lovely line about
"Brutes and braggarts may Have their little day. We shall never bow the knee."
That has a lovely air of "put down" about it.