Mixing unit (2; 102) for a mixer tap, the mixing unit (2; 102) having a generally cylindrical shape defining a main axis of the mixing unit, the mixing unit comprising: - a first inlet for a first incoming stream of fluid having a first temperature (Tf), - a second inlet (41; 141) for a second incoming stream of fluid having a second temperature (Tc) which is greater than the first temperature, - an outlet (43; 143) for an outgoing stream, - a control member (7; 107), - mixing means (13; 113) for mixing the first and second incoming streams to form the outgoing stream, the mixing means (13; 113) including a mixing chamber containing a set of mixing discs (13A, 13B, 13C) which extend in planes orthogonal with respect to the main axis, which are made of ceramics, and at least one of which is actuated by the control member, for controlling the flow rate of the first incoming stream and of the second incoming stream and thus adjusting both the temperature and the flow rate of the outgoing stream, and - thermostatic means which comprise: ∘ a thermostatic element (73; 173) which includes both a thermosensitive part (75; 175) arranged at least in part at the outlet, and a part (77; 177) which is movable in translation relative to the thermosensitive part along a closure axis (X73; X173), and ∘ a closure member (87; 187) for the second inlet which is connected to the part which is movable in translation along the closure axis, the second inlet being situated upstream of the mixing means (13A, 13B, 13C), the mixing unit (2; 102) being characterised in that: - an orthogonal plane (P71; P171) is orthogonal with respect to the main axis; - the orthogonal plane (P71; P171) and the closure axis (X73; X173) intersect; - the closure axis is inclined relative to said orthogonal plane and passes through said orthogonal plane. - a first inlet for a first incoming stream of fluid having a first temperature (Tf), - a second inlet (41; 141) for a second incoming stream of fluid having a second temperature (Tc) which is greater than the first temperature, - an outlet (43; 143) for an outgoing stream, - a control member (7; 107), - mixing means (13; 113) for mixing the first and second incoming streams to form the outgoing stream, the mixing means (13; 113) including a mixing chamber containing a set of mixing discs (13A, 13B, 13C) which extend in planes orthogonal with respect to the main axis, which are made of ceramics, and at least one of which is actuated by the control member, for controlling the flow rate of the first incoming stream and of the second incoming stream and thus adjusting both the temperature and the flow rate of the outgoing stream, and - thermostatic means which comprise: ∘ a thermostatic element (73; 173) which includes both a thermosensitive part (75; 175) arranged at least in part at the outlet, and a part (77; 177) which is movable in translation relative to the thermosensitive part along a closure axis (X73; X173), and ∘ a closure member (87; 187) for the second inlet which is connected to the part which is movable in translation along the closure axis, the second inlet being situated upstream of the mixing means (13A, 13B, 13C), ∘ a thermostatic element (73; 173) which includes both a thermosensitive part (75; 175) arranged at least in part at the outlet, and a part (77; 177) which is movable in translation relative to the thermosensitive part along a closure axis (X73; X173), and ∘ a closure member (87; 187) for the second inlet which is connected to the part which is movable in translation along the closure axis, the second inlet being situated upstream of the mixing means (13A, 13B, 13C), - an orthogonal plane (P71; P171) is orthogonal with respect to the main axis; - the orthogonal plane (P71; P171) and the closure axis (X73; X173) intersect; - the closure axis is inclined relative to said orthogonal plane and passes through said orthogonal plane.