Put in my new headunit today. Becker Mexico Pro (thanks Tom)

I have a few gremlins:

No remote central locking, "Headlights left on" warning tone does not sound when you remove the key from the ignition, no alarm beeps when opening the car.

I am sure it has something to do with the "red & yellow" wires, so if someone could enlighten me as to what is required it would be great

Your probably right about the red and yellow wires.

Think your need to swap then over.

i.e.red to yellow etc....