Hi
Know exactly how frustrated you might feel.  Had the same problem.  First of all fan was replaced, but every time cover put back on it light would flash again.  Then a new circuit board was added (almost £200).  This was then found to be faulty!  A new board has since been added.  So far no problems, but apparently combi boilers don't have as long a shelf-life as older ones.  Hope this helps somehow, also check for any small plastic parts which need replaced due to melting.
                
 Jeannie
                
 March 2010