Our boiler lived in a dedicated cupboard on the landing and across from our bedroom. The time switch was set to 06:00 and the initial " fan spin up and " whoomph " as the gas ignited acted as my alarm. Often I would find myself waking a minute or so beforehand. It was approaching the end of its days so I swapped it out for a heat pump that lives outside. I'm still waking at 06:00, I guess my internal clock has kept its program 🤔