London to Ankara is about 2,815 km and usually takes around 4h in the air. The track it follows runs over the British Isles, the North Sea, Western Europe, Central Europe, the Balkans, the Eastern European plains, the Black Sea, and the Anatolian plateau.
Air lifting over the Anatolian plateau can raise brief, light ripples at cruise; crews know these spots well and the movement stays gentle. Over the North Sea, the Black Sea, Western Europe, Central Europe, the Balkans, and the Eastern European plains the air is usually calm and settled. Nearer the British Isles the weather turns more Atlantic and the ride can be livelier for short spells, still firmly within the routine. This track threads jet-stream latitudes, so in winter you may feel a few minutes of light, choppy air high up; summer usually rides calmer.
For most of a flight this length you are at a steady cruise above the weather, where the ride is smooth; the livelier moments, if any, are short.