Hi Windsor .
All vehicles with central locking are wired so that in the event of a collision with both doors locked , the inertia fuel cut off switch automatically opens the locks . I agree with David that the rattle ( machine gun death rattle ) is a sign that the pin is broken in the door latch so im not certain that the method I suggest will work but there is no harm in giving it a try . With the boot open and the drivers door window down, manually lock the doors , then turn the ignition on but dont start the engine . The fuel cut off switch ( Inertia switch ) is under the engine inspection grille on the n/s ( passenger side ) of the engine bay . If you remove the grille to give easier access , give the body of the switch a firm tap , it should release the door locks . I tried this last year with a TF with a similar problem death rattle lock and it unlocked both doors .
John