Understanding UK/ Australia double taxation

Hope someone move can point me in the right direction...sorry for the long post! Am from UK and on a temporary 4 year 482 visa. Started work in Australia in Jan this year. According to tax rules I am still UK resident for tax purposes as spent April 23- mid Jan 24 in UK so more than the 183 days. However am also resident for tax in Australia. Being a 'good person' I followed the 'rules', completed the HMRC P85 notifying them that I was moving abroad and sent it off with my P45. I have a pension through Teachers Pensions which is paid to my UK bank monthly. I am fully aware that this is to be taxed by UK. Have just heard from HMRC by post saying they will tax my non-UK income (ie my Australian income) as I am still a UK tax resident. This will just be the bit from Jan this year to end of UK tax year which is 5 April. There are others I know who are working here under same conditions and in same time scale as me who tell me that they also submitted a P85 but have actually received a refund from HMRC and have been told they are no longer officially resident for UK tax purposes. Sounds like split tax year rules have been applied to them. Is mine different because of my pension? Aware of the tax treaty between UK and Australia so I know I won't need to pay tax twice but how do I go about claiming the tax back from HMRC as I will have already paid it in Australia? Should I be completing forms to claim this back -UK? Australia? or will this naturally right itself when I complete my Australian tax return later in the year? I have tried to understand the double taxation treaties articles but it's not exactly plain English and hard to understand. Wondering if I will also need to do a UK tax return although have never done one as always been on PAYE systems. The letter from HMRC asks me to provide them with details of my UK income for 2023-4 ( even though they have had my P45 and know what my pension income is as they tax me on it!) but does not specify 'tax return' so unsure of what format I should give the information. Assuming next UK tax year it won't apply as I won't be a UK tax resident at all as no days will be spent in UK.( although know from ATO my pension will only be taxed by UK; not Aus as I am temporary) How will HMRC know this? Grateful for any pointers. I feel like I am going round in circles and following a million online links that I don't really understand! Thanks in advance!

Hi MarjJ763,
As UK resident for 23/24 you are liable on your worldwide income for the whole year.
You will therefore need to complete a tax return for 23/24 to claim Foreign Tax Credit Relief for the Australian income for Jan-Mar.
Guidance for this is at:
Relief for foreign tax paid (Self Assessment helpsheet HS263)
As non resident thereafter (until you come back to UK) then no further returns required.
You may need to complete 1 for the year you return.
Thank you,