uh, depends on why each country went to war, maybe? (I'm half english half australian, chinese and portuguese origins)
But as a born and raised Aussie I would go home for it and support the aussies, but I can't imagine myself ever wishing pain or suffering on the UK. I live in England, I'm half English and love the place to bits...
mind you, the chances of England and Australia going to war - hahahahahaha! We are too busy fighting about the Ashes or the Rugby to give a toss about much else with each other...