Hi,
The personal tax account will not be an option for yourself in your current situation.
Form P85 would be the tax form required when leaving the UK for any refund in the same tax year and this can still be sent if you prefer. You can see information here:
Get your Income Tax right if you're leaving the UK (P85)
As the tax year has ended your records will automatically be reviewed and any corresepndance will be sent to the last address we hold for you on record. It maybe the case where you would prefer us to set a UK correspondance address to send anything to you.
You can go back up to 4 years to claim a tax refund.
Thank you.