CD changer in 04discoSD

I'm trying to install a cd changer in my wife's 04D2SD. It seems not to be prewired. I purchased the changer from the dealer. He did not tell me about any req'd data cable or brackets so I ordered these items from roverconnection. The cable fits the changer but does not fit the back of the head unit. The head unit is visteon and the changer, alpine.

What am I missing here?
Thanks in advance.

When I put in my changer (it was an aftermarket Alpine) i used an adapter byBlitzSafe, http://www.blitzsafe.com. It conveerted the standard ALpine CD changer cable into the plug that fit the Disco headunit. Good Luck.'

James