Have you tried removing the door trim and pulling on the connecting link that goes from the inner handle to the lock? This should release the catch if the door is unlocked.
Had a similar prob on my 4door mk1 when one of the rear exterior handles was not working and some comedian (who will remain unnamed) engaged child-lock on the door. Needless to say I wasnt impressed. Anyway, I was able to unlock and open the door by pulling on the lock/unlock and catch-release connector links inside the door.