A liquid soap dispenser having a permanent housing permits simplified insertion and replacement of disposable fluid reservoirs. The housing includes an actuator assembly which is cycled by a lever between first and second positions. The actuator assembly couples to a piston element of a piston pump carried on the reservoir. The piston element includes resiliently deformable fingers which act to secure the piston element to the actuator assembly for sliding movement therewith. If, on insertion of a replacement reservoir, the reservoir is positioned uncoupled from the actuator assembly, on first cycling of the actuator assembly the fingers deform to permit movement of the actuator assembly relative to the piston element and move towards a coupled orientation. In the coupled orientation, the fingers return to an undeformed configuration securing the piston element to the actuator assembly.