had the same problem christmas eve, husband spoke to various boiler people worcester wanted 300 pounds call out and wait 6 days. anyway,was advised at 4 30pm that it was due to low power due to high demand in cold weather, that it was the celliniod on top of the pump, raced to spares shop, who waited for me, plugged it in,perfect, cost 45 pounds. ok since.hope this helps. exscuse spelling
carol
December 2009