Edit. Yes when I turn it on at the mains. The boiler comes on, before flicking the switch ON on the machine. So the boiler is running all the time. Or has been.
If that is the problem you should be able to get it working while in that state and a temporary fix would obviously be to use the wall switch. Try priming and see if that does it.
Edit. Yes when I turn it on at the mains. The boiler comes on, before flicking the switch ON on the machine. So the boiler is running all the time. Or has been.
So replace main switch. Problem should be sorted.