What was found
(CAN) RIGHT AFTER TAKEOFF, THERE WAS AN ECAM WARNING MESSAGE "LAVATORY SMOKE DETECTOR". THE CREW DID A RESET AND THE MESSAGE WENT AWAY. HOWEVER, THE MESSAGE RE-OCCURED AND THE FLIGHT RETURNED IN CONSULTATION WITH LOCAL MAINTENANCE. THE CREW DECLARED A PAN PAN WITH ATC, AND WAS MET BY EMERGENCY VEHICLES. THE ACFT LANDED ABOVE THE MAXIMUM STRUCTURAL LANDING WEIGHT. THE LANDING WAS OTHERWISE ROUTINE. FLIGHT TAXIED TO THE GATE WITHOUT FURTHER INCIDENT. CABIN CREW STATED THAT THE SMOKE DETECTOR AT LAV D WAS GOING OFF WITH NO SMELL OF ANY KIND. LAV D SMOKE DET REPLACED AND CHECK SERVICE REF AMM 26-17-15, PB401