You can still claim your UK state pension but it's 'frozen' at same rate as when you leave UK - ie, if it pays 150 GBP per week today and you leave tomorrow and stay in Aus for the rest of your life, you won't receive any increases (if there were to be such a thing!).
Also visa - takes quite a while to get this processed and isn't cheap - but if you're not in a rush, shouldn't be a problem. You need to look at the Partner Visa (subclass 309 or 100). Easy to find more info on this via Aus government immigration website.
Can't answer about taxes, apart from what I pay on my earnings (too much of course!).
Cost of living is more expensive (depends on where you are exactly), and quality of life - to me - is what you make it.
Note that domestic and international travel isn't cheap - factor this into your plans if you're using to lots of breaks or long holidays.
Also check on how health expenses will be covered if you move here. Most people have private health cover and the cost of things work differently here - ie, some GPs will charge you and you'll get some of the cost back via Medicare, prescription prices can vary, etc. I find it confusing still, and non-urgent specialist treatment can get pricey. But again depends on whether it's covered by your insurance, or by Medicare, or solely out of your own pocket. I don't know how it would work if you were retired, or you wouldn't be treated as "retirees" as such.