The present invention provides an apparatus comprising a housing and a flexible reservoir adapted to contain a fluid and having a septum member formed from a needle-penetratable self-sealing material. The flexible reservoir is arranged within the housing in combination with mounting means arranged within or formed by the housing, wherein the mounting means engages the septum member to thereby mount the flexible reservoir relative to the housing. In this way a secure fixation between the reservoir and the housing is provided without having to interfere with the general flexibility of the reservoir, e.g. substantially the entire flexible reservoir apart from the outlet/mounting means may be arranged free to move relative to the housing, this allowing the reservoir to be emptied to a high degree.