Pump dispenser comprising a pump for dispensing fluid from a container to which the pump is attached, the pump comprising a pump body having a cylinder component and a body insert component, said body insert component comprising a top body collar and an inner tubular part defining with said cylinder component a pump chamber; the pump further comprising a plunger having a plunger stem and a plunger head and being reciprocable relative to the pump body in a pumping stroke; a lock-down mechanism comprising respective lock formations (2911',183') of the plunger head and pump body, the lock-down mechanism having a locked condition at a fully retracted position of the plunger in which the plunger is locked against reciprocation and an unlocked condition in which the plunger can reciprocate for pumping, and in which a release movement of the lock-down mechanism from the locked condition comprises a relative rotation of the plunger and pump body around an axis of the plunger, the lock-down mechanism comprising a threaded engagement between the plunger head and the pump body and the lock formations being respective screw thread portions (2911',183') on a radially-outwardly-directed exterior surface of a downward peripheral skirt of said top body collar of the pump body and a radially-inwardly-directed surface of a downwardly-depending skirt of the plunger head, and a catch mechanism comprising respective catch formations (296';88',188') of the plunger head and pump body which are engageable to prevent or inhibit a relative rotation of the plunger and pump body around an axis of the plunger for said release movement, each of the pump body and the plunger head having plural said catch formations (296';88',188') distributed circumferentially; wherein said catch formations of the plunger head are axially-extending inwardly-directed edges of radially-extending reinforcing ribs inside the plunger head having circumferentially-directed abutment surfaces, characterised in that said top body collar has a top face directed towards an underside of said plunger head and a central inner annular lip rising from said top face, adjacent an opening where the plunger stem emerges from the pump body, and said catch formations (88',188') of the pump body are radially-outwardly-projecting ratchet teeth (88',188') on a side face of said lip of the top body collar, each ratchet tooth having a ramp formation (884',1884') sloping outwardly relative to the circumferential direction, and an oppositely circumferentially-directed abrupt abutment surface (885',1885'), directed oppositely to said abutment surfaces of the plunger head catch formations; a said plunger head catch formation riding over said ramp formation as they rotate towards engagement, with radial deformation of the plunger head catch formation against a resilient force, until the oppositely-directed abutment surfaces of the catch formations (296';885',1885') of the plunger head and top body collar come into circumferential register and the deformation is relaxed on making the engagement. a ramp formation (884',1884') sloping outwardly relative to the circumferential direction, and an oppositely circumferentially-directed abrupt abutment surface (885',1885'), directed oppositely to said abutment surfaces of the plunger head catch formations;