"I had a Drayton SM1 mechanical timer. It was there when I moved in. What a beast! Noisy, not user friendly and only 2 settings! It packed up... Replaced it with the LP711 wich is nearly £100 cheaper, silent and so many more functionalities. Straight swap as the back plate is the same. Undo the two bottom screws and off you go. No wiring required. it was even already set to the correct time. Very pleased with it so far."