My passenger front door is jammed shut !?

The passenger door on my wifes rover 25 is jammed shut,I have managed to get the door trim off and have disconnected the central locking to prove that it works and it does the fact of the matter is that the door latch is seized and no matter what i do I cannot get it free,I suspect a broken return spring on the latch as the central locking seems to be o.k. It's absolutely