On holiday recently in Madeira and my wife and I went twice to the Istanbul. Both times we had a fantastic meal, the grilling of the meat, fish and seafood was superb and if you are lucky you can see it all happening in front of you. The staff were really friendly and helped if needed. I would throughly recommend the restaurant.
Go for the "set meal" including either fish or meat kebab, you will not be disappointed. Starter of mixed mezze excellent but filling. Lovely atmosphere & staff, we visit every time we are in Funchal