Hi Soo,
If there is a tax treaty between the UK and your country of residence, please check if there is an article for self employment or other income.
It is most likey that as you are not UK resident when undertaking the freelance work, it is only taxable in your country of residence.
The interest arising in a UK bank account, would normally be taxable in the UK, but would be treated as disregarded income, when you are not resident.
If the interest exceeds £10000, you would be required to declare it in a Self Assessment tax return.
Tax treaties
Thank you.