We did this last October. It has taken me a year but I can now see it was absolutely the right move.
We had been there 8 years, both my children were born there. We are all dual citizens. We moved with a 3ur old and 1 year old. We wanted to do it before eldest started school so to cause the least disruption.
We have finally agreed a sale on a perfect home for us. Like you, we could never have afforded to buy in the area we wanted, in Perth.
We have bought in the south east, in a lovely village five miles from a city. Even there it is significantly less than what it would have cost for the equivalent in in aus. Yes brexit is coming and we may get burned but we need a home and worse case scenario we will just have to stay put in our nice house and ride it out!
Pp mentioned cost of moving, which didn't affect us as our relocation was paid for but is worth doing the maths on. We made a lot of money from moving through selling 2 cars that were worth a lot more than they sell for here and buying one much more reasonably priced family car. We also were able to cash out 2 lots of long service leave from our employers.
There are a lot of things I miss and I was heartbroken for the first six months but it was amplified by the fact we moved for winter and mainly I just missed my friends terribly. More than anything else.
I've since made new friends and been really surprised how much easier I have found it to make friends here than there . Particularly num friends. People seem so much more on my wavelength and easier to find a way in with whereas I often felt like I had to work quite hard at new friendships there. The area I lived in was very image conscious and money conscious and I found that hard work. Everyone found it really important to be eg driving a new car, dressing their children really stylishly and I found that quite hard work. The playgroups here are so lovely, never really experienced anything like them there. I've made such great, supportive friends who I can have such a laugh with, in such a short space of time.
Finally, I have seen my children's relationships with their grandparents really blossom. My 4 year old has her own in jokes with my FIL and calls him get best friend! They are also growing up with cousins, uncles and aunts.
Feel free to pm me if you have any questions about making the move! I totally get where you are and we wrestled with the decision for a long time.