Hi,
As your UK military pension is a government pension, it will remain taxable in the UK, even when you are resident in Australia. Your state pension will not be taxable in the UK, nor will any private pensions you may have.
As you will not be resident in Scotland, you would revert to the national rates of tax
You will need to complete form P85 to advise HMRC that you are leaving the UK. You can submit the P85 here:
Get your Income Tax right if you're leaving the UK (P85)
You will need to create a government gateway user ID and password, if you do not already have them. If you are unable to di so then there is an option to print off the completed form and post it to HMRC.
Thank you.