Hugster, had identicle problem after replacing the ignition barrell in my Son's Saxo. There are three electrical connectors on the new switch, a black, brown and a grey plug. After closly looking at the old switch i discovered the new one is wired differently. You need to plug the black one into the gray socket on the car, and the gray plug into the black socket. they will fit with a bit of gentle persuasion :-) . Do NOT fit the black plastic cover yet , this is the immoboliser arial . This detects the transducer fitted in your ORIGINAL key. Place the old key next to, or inside, the black cover - well away from the new key before you turn the ignition on. The car should start as normal. At sometime You will need an auto electrician to reprogram the immoboliser with the new key, or as in my case I taped the old key into the cover and tucked it behind the dashboard, well away the new barrell . Hope this helps
Ian
February 2009