audi bus input on concert CD

i am wanting to wire in TV head rests and sun visor TV's too, and have the audio comin thru the head unit, via the CD bus interface,

is there a way of doing this without buying the bus interface which is £70

i have i wire that plugs in the back to give me some phono ends for the audio input but i gather i need to do sumat to trick the cd player that there is a cd changer attached, as when i choose the cd changer option nothing happens, is this coz my head unit dont support the cd changer or is it because the HU knows there is no changer attached!!! plz help