Hi Ellenbf42 F,
Please have a look at the double taxation tax treaty between the UK and Australia:
2003 Australia-UK Double Taxation Convention - in force Updated 31 May 2021
Article 10 covers dividends.
For most individuals the relief rate is 15%.
You can find tax treaties for the UK and other countries on this internet.
Search for 'tax treaties uk / xxxx'.
The FTCR will be up to a maximum of 15% of the Australian dividend received, depending on how much UK tax is payable on all of the dividends in the tax return.
Thank you.