Every time the central heating comes on the pipes start making funny noise. We have a combi boiler and hav bled the radiators more often than i care to remember. Please help me as it is keping us awake at night its that bad.
That's probably all it is, the pipes rubbing against joists, floorboards and other pipes, you could lift the boards and insulate/lag the pipes and enlarge joist notches if the pipes are a snug fit. Also clip the insulated pipework to the joists so that they don't touch and rub on floorboards etc.
Nothing to worry about - although the noise may be annoying.