Everything is back together and working because of your sprinkling of wisdom. Obviously my grasp of the nature of a thermostat is somewhat sketchy. Thank you for helping me at this stressful moment my Xmas cheer has narrowed down to feeding my old-ish parents on the day, and I was staring down the barrel.
My other half would also like to thank you as she was hiding in the front room for most of the afternoon!

