Worcester 28CDi 2 yr old ..was working great. Had to unplug for a few hours while electrician put some sockets in (unrelated downstairs) but now ...Heating fine, but hot water either runs for a few minutes or not at all - I can override it by switching on and off and pressing reset and "learning mode" and "override" buttons - but it still runs cold after 3-4 minutes ..these buttons arent expalined anywhere either ...wife really b***ching, but wallet really empty ..please help !