Ford Focus 2001 passenger door problem?

My central locking has been playing up for a little while now. Sometimes while driving the doors unlock themselves or lock, and I've always unlocked the door with the key. I don't know if it has remote access or not, I've never tried it.

Now, I can't lock the passenger door at all, either manually from the inside or outside with the key.

Would be grateful of any help or comments please.

Thanks

Jools