an idiot
Well it has become apparent that i’m an idiot. Firstly somehow in the confusion of moving house it would seem i have left the current clamp attached to the old house mains …. meaning my home monitor/smart meter is now not so smart and i need a new current clamp.
Secondly the python program works ok in py2 not py3 which is strange as i tried to write it in a such a way that it worked for both, and on tests on the original pi it worked ok but after transfer to a new pi with a fresh install of Raspbian Stretch Lite it does not like python3.