Vaillant Boiler completely silent when should be firing!?

My boiler is a Vaillant VC GB 142 EH (GC No. 4104409). Usually when it fires up, there is a whirring, then it fires. But now it is completely silent, and obviously not even trying to fire!! There is power being supplied, as the red power switch is illuminated. Can anyone suggest what the fault could be?
I had an issue with a sticking pump last year which was freed, my initial guess is the pump has failed.