[Neil]

You said the engine will not turn over - do you get any noise at all? Switch your lights on and then try to start it. Do your lights dim at all. If they don't I would say that the starter is not trying to turn the engine over at all. That could be a solenoid problem or it could be an immobiliser fault. Do you have a spare key? - if so try and start it with that. What car is it as well please - the more info you can give the more we can help - is it petrol or diesel - what reg/year is it.