Hi,
If you return to the UK, you would need to review the statutory residency tests here:
RDR3 Statutory Residence Test
If you meet the criteria to be tax resident in the UK, then you would be required to submit a Self Assessment tax return, to declare your overseas income and gains. Up to 100% foreign tax credit could be claimed on the onverseas tax paid.
If you are not resident in the UK, then your overseas dividend is not taxable in the UK, however any interest that the dividends generate would be taxable in the UK, as disregarded income.
If you are not resident in the UK and you do not have any UK income, then a tax return is not required, as none of your overseas income is taxable in the UK.
If you have UK property which you rent out or dispose of, then a tax return will be required.
Thank you.