An assembly for manufacturing a cartridge for regulating cold and hot fluids to be mixed, includes a pre-assembled base module, with a base, which encloses a mixing chamber with first and second inlets, for a cold fluid and for a hot fluid, respectively, and an outlet for a mixture of the cold and hot fluids, a slide, which is movable in the chamber so as to inversely vary a flow of the hot and cold fluids, and a thermostatic actuator arranged in the chamber, which moves the slide to a position corresponding to a pre-set temperature for the mixture. The assembly has at least two specific modules from among a single-control module, a sequential module and a dual-control module, each module being pre-assembled and including a housing suitable for being attached to the base, and an adjustment member movably mounted in the housing.