The engineer has been. The issue was cleared by running the hot water tap and then rapidly turning on and off the cold water inlet valve. This fixed the issue.
I asked to see if there was any drip of water and it appeared completely dry.
Engineer thinks that the incoming water may have had some dirt in it. He asked if there’s been work in the area on the water mains which may have caused the issue.
I will monitor it.
thanks for the help too, much appreciated.