Boiler query? - am I being ripped off - PCB enquiry

[r12las]

I know nothing about boilers so I'll explain:

Last night the boiler went off (I put central heating on 1st time yesterday - I don't think it went on at all) and had problems reigniting, but was on phone for help and it reignited (typical!), by the afternoon it was off again and I couldn't reignite.
Called someone out, they looked at it and said they ruled out the fan as it worked when not connected to the PCB or something, but it was the PCB that had gone, what are anyone elses thoughts?
This is my first experience at calling someone out (used to be tenant) and obviously I don't want to replace unecessary parts, look forward to responses...(the boiler is NF fanned flue gas heater, and provides hot water and central heating)

 

[COG]

The make of boiler and model would help not just the type. Its not common practice to test a fan as you said and if thats all they tested then forget about them. your ign sequence will be demand, fan run, fan established(usually a air pressure switch), then ignition and pilot gas followed by flame detection then main gas,. At which point do you have failure ?