Hi, we are in Australia too applying for a first UK passport (dual citizens). The big delay for us has been the gap between Royal Mail delivering documents (signed for in Durham on 14 March) and being officially received (over 4 weeks later).
Below is our progress so far:
Application being processed 2:31pm on 14 April 2022
Documents received 12:21pm on 13 April 2022
Application received 5:45am on 24 February 2022
Identity details received 5:44am on 24 February 2022
Email sent to person confirming your identity 7:25am on 22 February 2022
Ask someone to confirm your identity 6:59am on 18 February 2022
Application submitted 6:59am on 18 February 2022
Elsewhere on this forum you will read that HMPO has said the 10 weeks processing time is from when they receive documents, but in practice it seems to be extremely variable and unpredictable. (In contrast when my daughter applied for hers in 2019 the whole process took exactly 2 weeks from posting everything off and receiving the passport!)
I realise our situations are slightly different but hope this helps give you some idea about processing times for overseas applications from Australia.