The Turkish consulate states this:
Please note: tourist visas do not give you the right to take up paid or unpaid employment or to reside, or to study (including student exchange program) or to establish yourself in business in Turkey.
If one wants to stay longer than 90 days then just get a RP for 3 months, works out a lot cheaper then a plane ticket out of the Country and back again and doesnt effect your residence in the UK.
You become a non resident of the UK if your visits to the UK do not average 91 days or more a tax year over a maximum of four years.
So a person who spends more than 91 days in a tax year in the UK is still resident of the UK.