Rover 25 diesel 2001?

I have fitted a hands free kit to my sons Rover 25 by taking the radio out and wiring the kit into the black, blue and red wires at the back of the radio. The car kit works great but now I cannot get the car started. The engine turns over but wont fire up, I have even taken the car kit out and rejoined the wires up again and checked all the fuses but still no go.
Any ideas? Have I missed something?