I’m confused- we use boiler and hot water heater synonymously where I’m from (uk) so I use them interchangeably. What is your boiler doing- is this just house heat? Hot water radiators?
Didn’t realize you were English - I am also, just happen to have lived in the US since I was 8. My house has hot water baseboard heat so boiler = furnace. Basically circulates oil heated water. Hot water heater is electric and serves showers, tubs sinks etc.