Working for German company, occasionally from home office in UK

I want to move my family back to the UK but keep working for a German company. I will become dual tax resident, my employer will keep paying my german tax, I will retain an apartment in Germany. I think I must declare to HMRC how many days I work from the UK and pay UK tax for these, and claim this tax back from the German authorities. Is this correct, and is there a maximum or minimum number of days that I should work in the UK to do this efficiently? Is my interpretation of what I should do correct?

Hi

You would need to review the guidance on residency, to determine how this income will be taxable.  
If you are taxable in the UK on the employment income arising while you are physically in Germany, then you would need to declare this income in a self assessment tax return and claim a foreign tax credit.
 Please have a look at 1. Statutory Residence Test (SRT).

Thank you