A retrofit adaptation or conversion of a standard container, an adaptor neck or collar fitted to a standard top access port, such as by a threaded or bayonet interconnection, with an intermediate sealing ring, the collar providing an extended mounting for a liner inserted through its top mouth, manually or with the assistance of a tapered cylindrical guidance mandrel (not shown), the liner being configured as a open-top bag whose top edges are brought over a circumferential top flange of the adaptor collar to present intervening contact sealing faces for a top closure plate held in position by a circumferential 'C'-clamp, such as of a standard format used for barrel top fittings; one outer side of the liner being laid over the upper surface of a top flange of the adaptor collar, a top closure plate overlying the opposite inner side of the liner, so the liner is sandwiched between otherwise mating flanges respectively of the adaptor collar top flange and the top closure cap plate to achieve a generous annular double seal; a flange clamp locates and captures the juxtaposed flanges with the intervening liner and when set secures them firmly together, the top cap carries a delivery conduit or spear fitted through a top opening, such as with an interference push fit or threaded joint coupling, with a demountable coupling for a delivery feed line upon final installation; in one construction a dispenser is configured as an outer pressure vessel (12) with one or more internal liner bags (11) for respective content one or more content pathways a selector valve connected to the content pathways for selection and proportion mix, a pressurisation port in the container for charging the container externally of the liner bags and thus the content to promote discharge through the pathways a bleed valve from a pressurised gas supply for selective gas injection at or close to a point of dispensing with a facility to pre-mix and feedback the pre-mix to a dedicated liner bag; similarly with pre-gas injection; a plastics liner bag could be integrated with a plastics conduit and wrapped around the conduit as a cartridge format, for insertion in a port in a pressure vessel wall.