Anyway,did some searching on here & the `net,and it looked like a fiddly job & needed the whole lock changed.Heres how i just fixed it.Mine is a 2003 53 hdi estate SE.Rear elec windows,remote central locking.Puddle lights in doors.
Pull front seats foward to give yourself some more room.Undo top torx screw on the inside door handle.Remove lower cover blank from door handle and remove screw.Just pull the bottom of the door card gently away from the door.Then pull and lift the door card off.I undid the window switch(now i have to put the grumbings back in it that fell out
)Disconect puddle light & i put door card out of the way.Peal back the foam cover on the door to expose the door lock.If you look into the door at the door lock,its mostkly covered in black plastic.In the middle of it is 1 torx screw.Hold a screwdriver or something long onto the head of the screw & give it a few taps with a hammer.Try locking/unlocking the car,& hey presto,the door opened.Hitting the screw releases the deadlock.I then unpluged the plug in the door jam,diisconnecting everything to that door.You will have to unlock that door manually,but it works fine & opens & locks fine,just no deadlock though.Hopefully good enough for the mot as they only need to open the door
I will post a pic of the lock & screw as soon as i can work out how to do it from my new iphone 
Hope this helps anyone.