Hi, clearly a common problem with peugeot 106s, I have the same problem with both driver's side and passenger side front doors on a car I just bought off ebay.
The good news is, you can get the door trim off without having the door open - bit fiddly and there are loads of screws to undo, but it will come off. This gives you a smallish area to work with, but big enough to get your hand in. If you can somehow get the door open it becomes much easier, because then you can get the whole mechanism out and physically see and understand how it all works!
I have fixed my passenger side door simply by good old-fashioned WD40 - try this first! The problem was that when you lifted up the handle, the moving part that moves up to open the door was then not moving down when the handle was released. Having freed this up with copious amounts of WD40 it now works fine.
Am still working on the driver's side door...different problem here, in that when you lift the handle from inside, it knocks down the locking mechanism. It works fine when I pull it out of the car, but not once I've put it all back together!
Anyway, good luck to anyone struggling with this common problem, I am no engineer but hopefully my comments will help somehow, maybe!
Ian, August 2007