I very much agree with nun on this.
You will be a UK resident in the UK, paying tax on your worldwide income.
You're also a US citizen, and therefore you pay (file) tax on your worldwide income.
If you spend 4 or 5 months in the US each year, plus maybe 2 months in Australia or travelling, you're still a UK resident if that is your only 'home'. You become a UK 'snowbird'. There's nothing unusual about this as many Brits spend the winters in Florida.
You may handle this as you decide, but the easiest way is to pay all tax to the UK, then take a credit on the US return (treaty provisions aside). You qualify for all the usual US treatment of citizens resident abroad, including higher 8938 limits, but 8938 only concerns accounts that are 'foreign' to the US, not US accounts.
Therefore, my advice would be not to file the US return with a US address. Your proper address is in the UK. The US address only an 'address of convenience' for US accounts.