If the radiators heat normally but there is no hot water, the likely checks depend on whether you have a combi boiler or a system with a hot-water cylinder. On a combi, the boiler needs to detect hot-water demand and divert heat correctly. On a cylinder system, controls, valves, thermostats and the stored-hot-water circuit can all be relevant.
Check the simple user settings first, including hot-water schedules where your system uses them. Note whether the water is completely cold, only lukewarm or becomes hot intermittently.
Because the heating side is working, a targeted diagnosis can often isolate the problem more quickly than a general 'boiler not working' call. Doherty's Glasgow boiler repair service can assess hot-water faults on combi, system and regular arrangements.
