It appears that replacing the coils solved the issue, at least for now. What was happening, after a cold start with nothing in the dryer it worked fine for about 5-10 minutes and then cycled off. Then when it was supposed to cycle back on, at the same time the glow plug started to glow a buzzing noise was present. Then no ignition and glow plug went out and the buzzing stopped.
After replacing the coils from a cold start same thing, but when it cycled back on, no buzzing, the glow plug glowed and the gas came on and we had ignition.
My wife is going to do a few loads of laundry tomorrow, so we shall see if there was an underlying issue.