Hi there, thought I would reply as subject is a hard one and it may help to hear both sides. As much as I love the lifestyle and space Australia affords my family but it does come at a high price.
rent for at least one year to see how you cope, Uk house market is not great so rent it out, it is pretty emotional the first year, a bit like a honeymoon period and then the reality sets in. There are many lovely places to visit, allow sometime to travel around if you can afford to, I would explore a bit before you settle on an area to live, think of the local climate( is it hot all year or humid, does it have a winter) local job opportunities, schools etc.
It may help joining a mother/toddler group to met other mums and make some friends. I would think carefully about where you want to move to as it may be very different from where you come from, we live in a quiet area near coast so regularly go to Sydney for a city fix. So try to strike a balance of enough to do without it being too quiet or too busy, city life is full on here too.
You definatley get more house for your money although we are catching up and depending where you choose might live near the sea which is a bonus.
I along with my other siblings all live outside UK, my parents only had my children in UK as grandchildren and adore them but for pretty much the same reasons as you have left UK for greener pastures.
We have been here nearly 4 years and making good friends has been a little slow, swapping schools(eductional reasons, not to make friends!) helped, kids attend a school with quite a few naval families so a balance of Brits and aussies a little better, we are lemmings us Brits after all.
I do miss my parents badly, my parents are about same age as yours and not sure I could leave them if alone, it is horrendous when they leave after a visit, xmas, birthdays are pretty sad too.
I still get homesick, sometimes I think I want to go back, as my kids have got a little older I would like to return to work but locally it is very poor for jobs. I will say watching Uk does not help be warned you look back with rose tinted glasses.
I would say give it your best shot, what have you got to lose? A great experience, a life changing opportunity or living with a what if...
I am not sure if I helped your or me, but better to have tried than failed to try at all.