X5 rear doors central locking - need advice

[Solo Man]

Guys, the central locking on the two rear doors on my 2003 X5 3l diesel are not working. I was thinking of getting two aftermarket central locking actuators and fitting them in place of the "broken" ones on the car. I was warned that maybe that would affect the cars programming for the central locking and alarm system. Is this true or can i fit these aftermarket actuators (or make them fit) and open the rear doors with the remote that comes with the aftermarket central locking? I was thinking of using a live and earth off the standard central locking to work the aftermarket ones. Will that confuse the cars system?
Knowing BMW the genuine actuators probably cost R1000 plus each!!
So shoot me for fitting aftermarket parts to my car!!