Abstract: Modular service unit (10A) comprising a pair of elongate light fitting EACH comprising a reflector housing (14) having one or more light tubes (24). Either a bridging plate, or an intermediate housing (26), is releasably attached to or supported by adjacent longitudinal side edges (34) of each reflector housing (14), and forms a structural part of an auxiliary service facility. The auxiliary service facility can include, for example, air conditioning ducts or diffusers, (17A), five alarm detectors, fire sprinklers with flexible pipe connections, speakers, security sensors, and secondary light fittings. A plurality of modular service units may be incorporated in a suspended ceiling.