Potterton Suprima 50 - Pilot won't light?

Lovely flashing red light after three or so attempts by the boiler to re-light the pilot. Reset just restarts the whole procedure again - fan whirs, ignition sparks, no sign of a flame.

From what I've read this boiler has been fitted with a later PCB as it only has one light and the manufacturers manual shows two (one red and one green).

So far I've verified that it is sparking (I can see it).

I've tried letting it run through the startup cycle with the main compartment open (as suggested in one other post) to check the fan/air pressure switch) but that doesn't help. The fan is running though.

I can't find my multimeter (deep in the loft somewhere :S ) so I can't test the DC over the solenoid wiring and the same applies to my soldering iron so I've not bothered removing the PCB to see if the joints look dry (yet - that would change if anyone were to say that it's almost definitely the PCB).

I'm happy to call a Corgi registered guy out but I'd like to make sure that I've eliminated everything that I can try first. I'd also like to be able to give him a fair view of what I've tried so far and then let him decide how much of what I say is relevant.