heating?

Hi and can anyone help please?we have Glow-worm spacesaver50bf for our cent-heating which had been working fine,the only job we ever had done was about 18mths ago the pilot light wdnt stay alight got the engineer in and I believe he changed the thermocouple-all was well upto this sunday we had realy strong wind/rain and our boiler vent is down a narrow passageway between houses,on Monday morning I woke to a cold house?the boiler hadnt started from the auto-clock setting and the pilot was out-tried to light it but the piezo-ignitor dsnt spark,just the once from umpteen pushes-may the spark gap have grown to large or isit the ignitor or any other ideas gratefully received-Paul