Thanks for your post - I am Sam and I am one of the UK tax experts here on Just Answer.
Straight away I am drawn to the fact you state that you have had business tripe back to the Uk with your UK employer - these do create a Uk tax position that would need reviewing as only visits back to the UK (none of which should be for work purposes) less than 91 days are [permitted for your to be treated as not resident for UK tax purposes and exempt from UK tax.
These visits for work purposes, unless for meetings or training ill need to be declared to HMRC
Next lets look at the reason for your post. You ask
1. What are the UK tax implications if I resign my employment in Dubai, UAE with no on-going employment and return to the UK on 26 November 2016?
Then you will be treated as resident for UK tax purposes on 26/11/2016 - and be liable to UK tax on all or any future income (other than the situation regarding other work visits which I mentioned already for the period prior to your return)
2. What are the UK tax implications if I return to the UK on 26 November 2016 and continue work with my current employer in the manner described above? How long can I receive income paid in the UAE without incurring UK income tax liability?
Same as question 1 - you will be treated as resident from the date you return to the UK to take up this continuation of employment so liable to UK tax on all and any income from this date in the UK and this will be treated as foreign income as will still be paid from abroad, but liable to UK tax due to your physical presence in the UK as a UK citizen.
3. Can you advise if I can make use of any unused days of previous years' entitlement to stay in the UK for a period of up to 90 days to be carried forward for the current tax year?
No each year is looked at in its own right its just less than 91 days for each UK tax year, if the days are not used they are lost.