I will report back when I have used them.
I spotted these earlier this year on The Camera Store TV which looked interesting: http://www.theheatcompany.com/en/gloves/heat-3-smart but to be honest, I just use some regular medium weight hiking gloves and keep warm by moving. If I spent more time in a hide and less hiking I would have looked into them more.
This is their video review of them:View: https://www.youtube.com/watch?v=EW5WYxGv7jg
£120 for a pair of gloves!!!!!!!!!!!!!!