KatieKitten...
I moved from the US to the UK last year...it's been the BEST move I ever made. But I have to be honest and tell you that it was quite difficult and expensive. I'm not sure exactly what it would cost you to move to Australia from the UK, but I think one of the major mistakes I made when moving over here was that I didn't plan things correctly, which ultimately ended in me not being able to bring my cat with me and she ended up being put to sleep last month, so if I can make any suggestions, the one thing would be to get all the facts and costs for EVERYTHING!!! Because even what may seem like the easiest and smallest thing may be really difficult and expensive. For instance, I didn't know what I would have to pay for my marriage visa, and I still am not sure of the cost of becoming a citizen, becoming a dual citizenship person. I also haven't found out what the tax laws are in the US, I heard that I still have to pay taxes even if I no longer live there, which means I would have to deny my US citizenship, which would be difficult for me, but these are just some of the things that I have found out to be a little challenging. And since you have a child, then I would think there would be a lot more that you would have to find out, like for schooling, etc.
In any case, I hope it all works out for you in the end. I have found it to be exhilarating to make a move like that, to a completely different country than what I'm used to, also because I have the most wonderful husband in the entire world! Good luck to you KK.
Michelle