A319 pilot reported receiving an ECAM message during cruise for Cond FWD Cargo Duct Overheat and a loss of B system hydraulic fluid. The crew advised ATC and returned to the departure airport.

Narrative

Dispatched with HP Bleed valve on MEL and HOT AIR valve on MEL (so hot air valve turned off per MEL procedure). Just about to level off at 34000' and lost all B hydraulic fluid. Then subsequently got COND FWD CARGO DUCT OVHT ECAM. The latter was unusual because the HOT Air switch was off and the valve was closed -yet it still showed over 200 degrees going into the cargo area - suggesting to me there was a duct leak or air was leaking past the valve. This in conjunction with the loss of B hydraulic fluid led to my decision to [request priority handling] with ZZZZ control and return to ZZZ. We performed all checklists and procedures and returned to ZZZ; complying with the overweight landing procedure and precautionary landing procedures in our QRH. We landed uneventfully on runway XX and had ARFF (Airport Rescue and Firefighting) look over the aircraft to make sure we were safe to taxi to the gate.Cause: It would be best practice to have maintenance clear as many MEL's as possible prior to dispatching aircraft because this compounds any other mechanical issues that may arise.