Central Locking Fun! i.e. Not Working!

I have picked up an old Discovery 1 for something to do, i.e. a project car while I am waiting for a chassis for my real project (Defender 110 1991 Rebuild).

I have the following problems with regards to central locking :

1. Using the Keyfob only the rear doors and the passenger front door lock and re-open.
2. Drivers door does not lock with the key at all or with the Keyfob, also button on door will not stay down.
3. Passenger side rear door does not open at all, locking system seems to work, i.e. the button on the top of the door goes up and down, but door will not open from the inside or outside door latch.

Any ideas as to what to check?

Take the door card off n see if all the gubins are in place..

And then lubricate and exercise the mechanism until it moves as it should.