Hi,
Please have a look at article 20:
UK/HONG KONG DOUBLE TAXATION AGREEMENT AND PROTOCOL , which covers self employment. it advises, that if you are in resident in UK while working for your Hong Kong clients, you are taxable on your profits only in the UK.
You will need to request a certificate of residence:
How to apply for a certificate of residence to claim tax relief abroadto claim a refund of tax from the Hong Kong tax authorities.
In the self employment section of the tax return, you declare your profits from your overseas income.
Based on the tax treaty, you cannot claim a FTCR, as your profits are not taxable in Hong Kong.
Thankyou.