London to Milan is about 981 km and usually takes around 2h in the air. The track it follows runs over the British Isles, the North Sea, Western Europe, the Alps, and Central Europe.
Air lifting over the Alps can raise brief, light ripples at cruise; crews know these spots well and the movement stays gentle. Over the North Sea, Western Europe, and Central Europe 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.
On a flight this short most of the time is climb and descent, so any small movements come early and late; the cruise in between is brief but calm.