Hello, I am Keith, one of the experts on Just Answer, and pleased to be able to help you with your question.
If you spend more than 183 days in the UK in any one tax year [6 April - 5 April] you are liable to UK taxation on your world wide income. You should register as self employed; the procedure can be found here:
At the end of each tax year HMRC will send you a self assessment tax return to complete. The income you receive from Hong Kong will be subject to UK Income Tax. As a citizen of the EEA you are entitled to a Personal Allowance, currently 11K, to offset this income. The UK has a Double Taxation Treaty with HK which precludes the same income stream from being taxed in both jurisdictions. This is achieved by means of tax credits, the tax paid in HK, if any, being allowed against the UK liability.
Just Answer protocol does not permit me to make recommendations of individual practitioners, but your return's completion would be well within the capability of any local practitioner and, quite frankly, you could do it yourself it is so simple. Just ensure that you maintain adequate records which you are clearly already doing.
I do hope that you have found my reply of assistance.