Cheers guys. There is no ISO socket on the back of the unit, just 5 wires. I presume 2 of these will be speaker wires (these match up colour wise with 2 of the wires coming off the loom, but the ones that come off the loom also have a second wire attached to them), the other 3 are then earth, constant live end ignition live I should think. If it would be any help I can let you know exactly what colour the wires are.