A control valve, and a control module including such a control valve, for selectively controlling a flow of pressurised hydraulic fluid from a pump in a hydraulically powered vehicle seat adjustment system. The control valve including a duct for pressurised fluid delivered from the pump, and a moveable valve member which selectively closes off the duct. The control valve also includes an integral set of contacts which are arranged to activate the pump to provide a supply of pressurised hydraulic fluid to the duct when the valve member is in the second operative position in which hydraulic fluid is permitted to flow though the duct. The control valves are preferably mounted within the control module which defines an internal chamber forming a reservoir of the hydraulically powered vehicle seat adjustment system. The control module is mounted upon a side valance of the seat as a single integrated unit.