I got locked in and thought I might have sat on the fob as pressing lock and unlock opened the drivers door,it happened again but key was in ignition, following advice I sprayed wd40 at the lock and inside the door, this seemed to encourage the machine gun type rattling referred to.
I have purchased a new mechanism for drivers door but also removed central locking fuse to avoid being locked in ,this means I can unlock drivers door with key but still need to press fob to disarm alarm.
Being without central locking on a car with only two doors and rarely with a passenger is fine for now.