I have exactly the same problem on a RHD car. I suspect the actuator as when I checked inside I could see it was trying to move when the system was locking and unlocking but it wasn't managing to push/pull the mechanism properly.
At least mine un-deadlocks sucessully though... (but not always, so I should fix it before ending up in your shoes.
Sounds like you can just buy an actuator and go through the trouble of getting the panel off is a PITA, but at least it is possible! The very best of luck.
Good luck, Nick