An assembly of a mounting support and an optical fibre connector adaptor (20) mounted on the support, wherein the adaptor has a connector-receiving axis and at least one lateral (to the said axis) mounting projection (25) on at least a first one of its sides, and the mounting support comprises wall members (not necessarily flat or continuous) upstanding from the support on both sides of the saidadaptor, which wall members on at least one side of the adaptor define mounting slots adapted to receive the said mounting projections of the adaptor, and wherein the slots are formed topermit movement of the adaptor between at least a first position in which the adaptor is supported with its said axis at an acute angle to the support, and a working position in which the adaptor is supported with its said axis lying substantially parallel to the support, and wherein the wall members define, in at least one of the said slots, at least one shoulder (30) on which one of the mounting projections (25) of the adaptor can be supported, and at least one resilient portion (35) of the wall member is arranged to retain that mounting projection removably on the said shoulder.