This thread is about a UK citizen actively wanting to become an immigrant so whilst you might think you're being clever, leave your political leanings out of it. You have absolutely nothing to offer in this thread, nothing. There is literally no value you can add.
OP, there are quite a few people actually living in Ozzie who have chimed in but you'll note that they don't all agree on all the same things. Part of that is personal and subjective opinion, part of it is shaped by just the sheer scale of the place (3 time zones!) and the differing views that provokes, and part of it is everything else which moving just about as far away as you can from the UK means to how your life will work out.
The most obvious things I can think of to investigate are:
(1) Housing - Sydney is expensive and its housing costs can make your eyes bleed unless you already have substantial rent or mortgage payments. In case you're taking this lightly, it might be an idea to jump on to one of the Property websites to see exactly what you're looking at.
I'd rather live out of the city, engineering jobs ie factories/mines and what not tend to be rural or at least semi-rural...I'd only be renting anyway as I don't think my lady would want to commit to a mortgage with out really knowing if she could handle being there.
(2) Job opportunities - I know nothing of current trends but Xordium and 1 or 2 others mentioned the health care side of things having peaked and now in real decline. Do your homework.
I'd like to think I could support us both and for her to not haveto work. Although she is more than capable, she's struggling to enjoy work in massively understaffed hospitals though, maybe it's different there?
(3) Cultural fit - All Australians are brilliant and they won't wait for you to ask. They will shout it at you but they will do it in such an infectious way that you won't think they're the asshat they perhaps are. More seriously - and this is a huge generalisation and one I won't apologise too much for - they're upfront, manners be damned, tell it like it is kind of people by and large. In my experience, of course.
I like that
(4) Distance - if you or your partner need to see mum or dad or the inlaws every Sunday for brunch then this will not work. Unless they come with you (do not do this). You can be back in the UK within 30 hours, you can skype in real time, you can call for very reasonable rates but you cannot pop round for a chat with your mates or go and check on your mum's cats.
I'd be happy going back for Christmas but she'd need 2 or 3 trips home a year I reckon.
(5) Health (related to 4) - if people you care about are very old or on the decline in terms of health then have a think about where you want to be.
Oz 
(6) Networks - one of the reasons we found the UK > NZ move so effortless was that my wife, as a kiwi, already had friends and family in NZ. A lot of ex-pats talk about isolation so bear that in mind when upping sticks to a place where you might not know a single other person.
I have a good friend in Dee Why who's been there a while now. Got some distant relatives in Brisbane too.
(7) Be realistic - it might work or it might not. It's pretty binary I think. Don't go with the expectation that it MUST work, rather that you hope it WILL work. the world is a really big place and different people enjoy living in different places.
If it just aint right I'd like to try Vancouver, but We'll be keeping our house in the UK anyway as a fall back.
(8) Try before you buy - for some reason I can't now see your OP as I type this and can't remember if you've holidayed in Aus. If you haven't, it's a very good thing to do.
Nver left the Northern Hemisphere. How do you cope with water going down the plug hole the wrong way 
(9) - Good on you! - even if you don't do it, or do do it and don't like it, I salute the fact that you're even thinking of it. Good for you.
Cheers man
