Hi alertik,
You will need to submit a self assessment tax return, to show your foreign Ukraine income and the tax deducted (this needs to be declared in pounds sterling) and the tax deducted on this income in the UK.
You will need to claim a foreign tax credit relief against the Ukranian tax paid, this will prevent double taxation ocurring.
You will need to review the double taxation agreement, which can be found at
Ukraine: tax treaties.
You will need to consider your individual circumstances and apply them to article 4 (residence).
This is the latest guidance on how taxation is applied and will help you determine your residence status for tax purposes.
If you need further guidance on this, you may need to consider seeking financial advice.
Thank you.