There will be a house distribution board with fuses or circuit breakers - a Consumer Unit - check it.
There will be a fused supply to the boiler so that it can be electrically isolated for maintenance - usually with a neon light - check it - often within a few feet of the boiler itself.
There may be (very probably will be) a fuse inside the boiler case - check it if you feel confident else call in a specialist from Yellow Pages or one reccommended by a friend or neighbour.
Good luck...
Peccavi
December 2009