Hi Garry, sure no problem mate, just explain a couple of points to me, the engine runs whilst the ignition key is in cranking position, hence the strater motor is still engaged and running, so please confirm.
secondly when you return the ign key to normal the engine cuts out, so this indicates that all else is fine except there has to be a wiring fault or a fault with ignition switch element, as a first guess, On ignition switches, there are contacts that are made during cranking position and there are contacts that are broken during cranking position, e.g. during cranking heaters are all switched off as they draw a lot of current so that most current can be direceted to the starter motor. so whilst cranking the ignition circuit has to remain intact, as well as when the ignition switch is brought to normal, where the heater supply (demister heaters) resumes. but does the ignition circuit stays ON, so check that when you switch On your ignition all lights are on when not cranking.