Hi Kirk, I did a quick check just trying to by-pass it. (Thanks for that tip Lemp!) Still no go.
I don't have any kind of tester, but I'm watching a You Tube video at the moment. He's saying if there is no clicking when you try to start the heater that the circuit board is probably bad. You are quite right though, I don't want to have to replace it unless I have to!
Pat