The income arose in the period that was overseas, so should not be included.
This would be the same for pensions relating to the overseas period paid after the overseas period ended.
You would count your 91 days from the date you arrived in the UK.
The accommodation tie guidance can be found at (RDRM11550 - Residence: The SRT: Accommodation tie
You would be considered tax resident from 26 Aug, as that is the date you arrived in the UK.