Send for a boiler specialist...
To get the pilot flame requires....
Fan running
Case fitted correctly
Pressure switch activated
Circuit board behaving correctly
Pilot gas valve opening
Electronic spark ignition
There is an overheat cut-out which you can reset - falls out from underneath - but in your case it will not have operated.
You can sometimes see the ignition spark through the observation window - hear it too - if you have the spark then the pilot gas valve is suspect and the other things eliminated.
Good Luck...
February 2016