Personally, I think there should be a hand held microphone (karaoke style) passed along the team members, who each in turn, sing a line of the anthem...that should get their team-spirit and/or adrenelin a-surgin'.
God Save the Queen is not only the UK national anthem but the anthem for our overseas dependencies. Their national teams stand and try to sing the anthem but the team may be composed of ex-pats who have qualified by living there for a number of years. These ex-pats may be any nationality typically Canadian, South African, Irish, Australian but as part of the team have to stand for the anthem. It can be quite amusing seeing some of them struggle with this.
Why do all these posters seem to think it is compulsory to sing the national anthem. For goodness sake we're not in North Korea, yet. If some players wish to sing that's fine. If others just want to stand to attention, or as close to it as some can manage, that, too, is perfectly acceptable.