Hi,
You will need to review the guidance at RDR1 (
Residence, domicile and the remittance basis: RDR1).
As you will be in the UK for more than 183 days, you are tax resident in the UK for the whole tax year.
This is where you need to consider split year treatment rules.
If split year treatment applies, then you only declare your UK income for the whole tax year and your foreign income for the period from the date you arrived in the UK to the end of the tax year.
If split year treatment does not apply, you are required to declare your world-wide income in the tax return for the whole tax year.
As you were in Hong Kong when you earned your employment income from your Hong Kong employer, then this income is not taxable in the UK, but for full disclosure, you would mention the income and tax deducted in the free hand notes box of the tax return (SA100 box 19 on page TR7).
Regardless of the outcome, a tax return will still be required.
Thank you.