Parked our '03 plate C3 at home, got out and tried to lock the car with the remote. No response. Checked all the doors and boot were shut, which they were, and tried again. Still nothing. Got second set of keys, thinking it might be battery failure, tried with the other remote, nothing. Tried locking the driver's door with the key, which worked, but all the other doors were still unlocked. Eventually turned the ignition back on and found that the "child lock" button was illuminated. Turned it off, then turned the ignition off as well. Tried again to lock remotely, and hey presto, the central locking was back in business. The owner's manual is pretty bad, as there is no real explanation of this side effect. Our car has the X12 ECU upgrade, not sure whether that's relevant or not, but I see there is another thread in this section about the car "remembering" the child lock state. If you turn the ignition off while the child locks are on, the remote central locking does not seem to function. HF