Hi. My name is*****'m looking at your question now and will post my answer or ask for more information here in a short while.
Take a look at the spreadsheet here in conjunction with the notes in section 5, cases 4 to 8, here. So long as you meet one or more of those cases criteria you will qualify for split year treatment.
There isn't much you need to do other then qualify as resident in the UK for 2016/17 and 2017/18 and as non-UK resident for 2015/16. Between 6 April 2016 and the end of December, you cannot spend more than 67 days in the UK. See Table F on page 66 of RDR3 or you risk having to pay UK tax on your German earnings.
I hope this helps but let me know if you have any further questions.
Follow up questions on the same topic don't incur any extra cost.
You will qualify under Case 5 as well if you meet the third automatic UK test over 365 days starting on your first day back in the UK. See paragraph 1.36. There isn't a specific number of days but, ideally, you should be looking to spend more nights in the UK than in Germany.
Being a director makes no difference really but it cannot harm you. You need to keep a record of where you are at midnight if you are outside the UK. HMRC aren't going to tell you aren't UK tax resident as that would be like turkeys voting for Christmas.
I have dealt with many clients who have either left the UK or returned to the UK or both. Sadly, I cannot take on clients through this site.
You don't need two accountants/tax advisers as far as UK tax is concerned. You may need someone to finalise your German tax position.
I'm not allowed to make recommendations I'm afraid.
I'd start by doing a search on Google in the area that you intend to live in the UK. Most firms will give you a free meeting to discuss your requirements so you can shop around. However, as with anything, you get what you pay for.