Callistemon21
Blossoming
Do Wales, Scotland and NI have ‘official’ national anthems? They each have their own football and rugby teams and I can’t imagine they all sing God save the current hereditary monarch.
Wales has an Anthem, Scotland sings an unofficial Anthem (but I'm sure the Scots could choose something more uplifting), N Ireland doesn't have one as far as I know.
Northern Ireland is the Londonderry Air, aka Danny Boy. None of them are official though, they are not recognised legally - not that it matters at all, they are adopted.
I think for England to change theirs though it will be people power at sporting events that does it, I don’t think a song is chosen, it’s more that it chooses you? (Eg why was Sweet Caroline the song for the Queen’s Jubilee?)