Focus [MK2] (2004-2007)
The Mk 2, code-named C307, uses the Ford C1 platform which is shared with the Volvo C30, S40, V50, C70, Mazda3 and Focus C-Max. Ford calls this platform sharing programme "Global Shared Technologies".
With regards to the car audio system, some vehicles used 12v accessory in the quadlock and some used CAN. The easiest way to confirm is to remove the factory radio and check if the harness has a 12v ignition feed included.
Pre-facelift Mk2 models were fitted with the 230mm wide Ford 6000 CD head unit, the Sony 6 CD changer head unit or even the Blaunpunkt TravelPilot radio.