2003 ford fiesta central locking

i have a ford fiesta 2003 with central locking and im attempting to install an aftermarket remote central locking unit. consisting of the reciever wires and the fobs. the units diagram says that it has white - LOCK WHITE/ black - Unlock and yellow and yellow/black bridged as the common what is the common wire spliced to as i cant see anywhere on the cars wiring diagram to indicate common. should i earth the common wires?

i have fitted the rcl unit and it works. my only problem is that i dont have the function to lock both the doors via the door pulls. any idea's?

hello did you have any luck fitting thid as i am going ot attempt it soon