Your boiler is making loud noises because trapped air bubbles are causing the water to rattle as it circulates through your heating system.

DIY fix possible

Turn off your boiler and wait for the radiators to cool down completely.Use a radiator key to open the bleed valve at the top of each radiator until water flows out steadily with no hissing air.Check your boiler's pressure gauge and top it up to the manufacturer's recommended level, typically between 1 and 1.5 bar.