You are over-complicating matters.

Ignore the speaker loom, in fact, if you are fitting remote central locking, ignore all the wires.

On a MK3 Escort, you need to add a remote locking solenoid to the drivers door locking pin (bit that moves up and down in the doorcard) as the drivers door is a master and has no locking motor of its own (it uses the owner turning the lock to actuate the other locks).

You wire in the "slave" motor you fit into the drivers door depending on your alarm instructions for an "additional motor". Only then will you have the locking working correctly.

If you try to tap into any of the original car wires for the locking, you will lock the passenger door and the tailgate only.