The engine not firing first time was probably more to do with the fuel temperarure than the glow plug.
Diesel does get a bit thicker in the cold.
Aha, fair enough. Still, however, curious as to why then my ignition coil light still doesnt light up even in the cold (snowing conditions). I did do a dashboard test and on the bulb test it shows the ignition coil lamp as working, but even in freezing conditions (i admit I havent had a thermometer out to test the cold, but snow on the car all night would suggest its minus conditions) it still doesnt appear. Should I just change the plugs and check the connections anyway? or is there another thing to suggest. Also my OBD2 scanner didnt pick up any faults.