Guesswork from an unqualified muppet...
I would suspect the fan - a boiler engineer should be able to test it quite easily - the bearings may be seized up (unlikely) or the motor windings open circuit (probable) or no power getting to the fan (maybe).
The boiler will not light unless the fan is working correctly - there's usually a pressure switch to check it - it's a safety thing.
Bad time for this - the specialists will either all be very busy or on vacation - you have my sympathy.
Good luck...
Peccavi, December 2009
