Changing flap setting below your minimum height for a stabilised approach should only be done in the event of a go around. The captains action of changing from flap full (not 4 - by the way) was very suspect.
Vref + 4kts is a little slow. If the autothrust has the engines spooled down then Mesti's method works. Too many people forget that even the A330 can be flown like a basic aircraft. The A330 is harder to slow down compared to the A320. However if you are slow (due to an unstable approach or windshear) you have to be very careful because the increase in thrust is large, although slightly delayed, when the autothrust is cancelled and the thrust levers are still in a high thrust lever angle.