The acquisition of any legacy in Turkey after the death of its owner, could be made through the courts by probate action upon the application of his relatives /heirs.
The heritage /estate/ property could only be passed to the heirs after a probate issued by the court of the province where the property is located.
Any legal action taken at the Courts of the UK (or any other country), could be applicable in Turkey only after the decision of a Turkish Court which recognizes and enforces the decision of the UK courts. Hence, a will could gain validity in Turkey after a decision issued by a court in Turkey.
A will is going to be valid in Turkey after some legal steps.
If one notifies his legal heirs (according to the will) about the existence of such a will, then they could follow up the matter after the death.
The probate letter /decision required to enforce a will in the UK, should be certified by the Legalization Department of the Foreign and Commonwealth Office (apostille) and then in the Turkish Consulate before being presented to the relevant authorities in Turkey.
After its certification process, the probate should be presented to the Court in Turkey in order to enforce it. Once the decision from the Turkish Court is taken, the will also be valid in Turkey and could become applicable.