Does anyone know if my car is pre-wired for a CD changer please?

Option 650 Single CD Player 59.57
Option 657 Radio BOOST 114.89
Option 692 CD Changer Prep 0.00

I know the head unit can control a changer, but is there wiring to the boot already in place? or do I have to run a wiring harness from the head unit to the boot?

thanks guys

John