Front passenger door stuck.

Just to preface this I've checked the forums, and tried most of the suggestions including giving it a hit. 

Front passenger door has locked itself shut. I can hear the central locking motor activating, but the door won't unlock. The pin has dropped below the level of the door card, and whilst using the interior door handle (very stiff) the pin will rise up, but door won't open. However the exterior handle does nothing.  (see attached video) 

Unable to remove door card to investigate as the dashboard overlaps it. 

Any ideas before I phone a mechanic.