As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LHR - FLIGHT ATTENDANTS REPORTED HEARING STRANGE SOUND AND A BURNT PLASTIC SMELL ABOVE SEAT 30G. FLIGHT LANDED LHR WITHOUT INCIDENT. PLACARD AFT UPPER RECIRCULATION FAN INOPERATIVE. REPLACED RECIRCULATION FAN AT AFW ON 11/23/2012. SYSTEM GROUND CHECK NORMAL OPERATION.