On a really cold day (scraping the frost off cold)
I will often wait for the glow light to go out, then turn off and back on again, so the glow plugs have a couple of goes of getting to temperature.
yeah that's what i was doing with mine but Mark the Brilliant Mechanic reckons that it just wasn't enough for this engine to have it turned on, then off, then quickly back on again,etc a few times over. He says the glow plugs were still warming up when the key is turned even when the light is off (hence why he thinks its some sort of communication problem) so I am better off leaving the ignition on when the light goes out for a few more seconds. I guess I'll find out tomorrow once it has sat overnight again.