Polypipe PB9700ZV 2 Port Motorised Zone Valve - Central Heating / Under Floor Heating / Boiler - Can Be Retrofitted to Other Manufacturer's Valves - Easy Connection - 22mm

The plug in wires rather than fixed to the unit made it easy to replace

This is a first class product. It only missed out on five stars as the micro switch isn't activated when the manual leaver is moved to the open position. There is almost almost 1 cm of clear space (see photo, the micro switch has a white dot painted on it by me to aid the photo.) This may be the case for all motorised valves for all I know. Otherwise it works brilliantly in normal operation.