Having established my 3port valve was faulty, I removed the motor unit from the valve and could hear something rattling inside it. I refitted it and used the manual lever to select the mid position and as I did I saw and heard a spark come from inside. Now everything is dead. Nothing tripped in the consumer unit, and the 13amp fuse in the supply to the heating is good but everything is dead, no lights on programmer or boiler. Where do I start?!