Passengers door not opening

[tomsettkent]

2004 reg Mini. Passengers door cannot be opened from inside or outside once locked. The central locking system operates on all other locks including fuel flap.
Problem started as intermitant fault but has progressed to complete non operation.
Have striped door and maually released door catch by dismantling catch assembly. With catch unit out of the door and electrics connected. The central locking can be operated and all works correctly, i.e. the window drops and catch releases the stricker plate. The catch can be reset and the central locking operates with both key fob, dash toggle and key in drivers door. It can again be locked and unlocked many times. However if the catch assemble is refitted into its working position then everything will work fine until the door is closed and the central locking operated. After this the door cannot be opened from inside or out. When the locking sytem is operated the lock makes the usual noise and the small black knob comes up to show it is unlocked, but when the door handle is pulled niether the window will drop or the door open !!
The door catch assembly has been renewed also the main control unit and the door wiring loom ! Might be cheaper to change cars than fix this one. Any ideas?