Glowworm boiler - got heating but no hot water??

Our boiler - glowworm compact electronic (can't find a model no.) - has stopped giving us hot water, but our heating still comes on?! For the past few days we got hot water if we switched another tap on, (eg. the bath tap when we were trying to get the bathroom sink tap to work), so we thought it might be water pressure. But now nothing works, even putting all the taps on in the flat!!! No hot water!!! Help as we've got a baby!