Sliding door stuck shut

Can anyone suggest how I can get one of my sliding doors to open, occaisionally it would be unable to open using the outer handle but was always accessible by using the internal handle to open it.
Sometimes locking and then unlocking it would give me access but this no longer seems to work either and it has now stuck shut,neither handles work, its a 52 plate 2.2jtd.
I've no idea how to even access the mechanism or what the root cause may be.

SNAP. I have the 2.0 jtd and my passenger door has done the bloody same thing. If you get an answer please please let me know

Hi. Managed it. Remove the door panels from the 2 screws behing the plate of the internal handel. one screw to the bottom at the back side of the door and one under the cup holder. pop panel of the door and you will see the mechanism. 2 black boxes with wires. top one is dead lock and bottom is for your popper button. disconnect the wires from the top box on both sides, passenger and driver. leave panels of make sure the deadlocks are pushed in to the box unit shut doors lock and open. try if no luck your door will open with the diagnol rod from the mechanism. Worth a try worked for me. Good luck