Engine wont start or crank with ignition

While driving slow, the engine just died, I could see the low level cooling indicator came on few seconds before. But the coolant level is fine. Now when I turn the ignition on the motor does not turn over, however the cooling fan comes on! This never happened before.
I have been using the car with two warning lights on, recently the first the SRS came on then the ESP, but I dont think either are the cause. When a engine diagnostic is fitted it just reads error in connection, we have tried with 3 different machines now. The ignition lights appear to be working normally. We checked the starter motor is good so is the battery Any ideas what could be wrong