I have a boiler in my attic that just heats the water for my bath and shower - the hot water has stopped.?

Possibly loss of electric mains supply to your attic boiler, such as through an electric fuse failing or circuit breaker tripping. Your first check therefore needs to be to the mains input to see if there is a voltage present there or not. If you measure it between terminals and find there is a voltage then problem is inside boiler circuitry, and may be mechanical or electrical.