I spent a couple of hours buzzing out the cable looms and pull testing crimps due to my head unit not working. Checked all the fuses and finally went down to Halfords who checked it and proved it was dead. I was sure it would be the fiat and not the stereo...really should trust this car sometimes!
Anyway just wanted to say thanks to Bockers for his FAQ showing the stereo cable loom pin outs, this saved me soo much time.