I was just a little younger than your son when my folks sprung a move on me - a mere 250 miles away. When you're a kid, that seems like the end of the universe and, well, Australia really IS the other side of the world. His big concern is, no doubt, being separated from his friends and everything he knows.

Do you know anyone in Oz with a boy about your son's age? The ideal situation would be to hook him up with an Internet pal over there he could get to know before you head over. It would also help him realize that there are ways for him to stay in touch with his mates back in the UK (assuming they are into online stuff).

But maybe there's also something to be said for letting him have his sulk about being handed such a big potential jolt to his nice, settled world. Some kids just have to work their way through things like this, without being constantly cajoled with "how much better a life it will be" and "how he'll make new friends." Right now he's faced with losing the only friends and the only life he's ever known. It's a big step - and it will take some time for him to adjust to it in his own way. Be there to answer his questions, but don't try to jolly him along too much until he's ready for it.
Cheers,
Bev