Aah, but ... Cargo Smoke warning comes via CIDS directly to the warning light - signal also goes to ECAM. I would believe the warning light ... it is from a reliable dual loop system. Any valve position is a result of the warning, not an indication of smoke/fire!
Dig out FCOM 3 and carry out the abnormal procedure .. fly at max speed to nearest airfield and land!
Flyman 35
then I would reset the cargo smoke sensor circuite brakers
SDCU reset is "on ground only" in the QRH.
All your actions indicate that you think the warning is false. Surely a sensible pilot would believe the warning to be true and act accordingly?