@Geraldineinoz, I'll take this one thing at a time.
UK Pension
The good news is that your UK pension should increase when you move back, because you'll get all the annual increases you missed out on. I recommend you also look into back-paying any missing NHS contributions, which will increase the pension you get. It's not too late! It's usually well worthwhile, but the UK Pension Service can help you work out whether you would benefit from paying them. I suggest waiting until you're in the UK to contact them, because the answer will be different when you're living there, compared to if you enquired now.
Australian pension
Are you sure you'll lose it? I can believe you'll lose it temporarily, because once you sell your house, you'll have money in the bank and then you'll fail the assets test. However once you've bought your home in the UK, you might be able to get the Aussie pension again. So I wouldn't consider it a lost cause -- keep in touch with Centrelink and let them know when your circumstances change, and see what happens.
Superannuation
Talk to your husband's superannation company and see if they'll pay the income stream into a UK bank account, or whether they'll have to continue paying it into his Australian bank account. It's no great problem if they pay it into an Aussie account, because then you just use a company like Wise to transfer it when it suits you.
The bad news is that his income stream (and your other pensions and income) will be taxed by the UK taxman, but the good news is that it won't all be at 40%! You'll each be liable for the same income tax as every other British individual, i.e. no tax on your first £12,570, then 20% tax on income up to £37,700. Then it's 40% on anything above that. There's no tax exemption for pensions like there is in Australia unfortunately.
House Sale/Investments
If you sell your house and put the proceeds in an Australian bank account before you leave Australia, the money is just savings and won't be liable for any British tax. If you have other investments, or if you delay the sale until after you've left, it may be a different story and you should get some professional advice.