Doha to London is about 5,241 km and usually takes around 7h in the air. The track it follows runs over the Middle East, the Anatolian plateau, the Balkans, Central Europe, Western Europe, the British Isles, and the North Sea.
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 Balkans, Central Europe, and Western Europe the air is usually calm and settled. Above the Middle East daytime heat can stir shallow thermals lower down, but the air smooths out at cruise. 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.
A flight this long spends hours at a high, smooth cruise. Even when one stretch is bumpy it is a small slice of the whole trip, and the aircraft treats it as routine.