I've finally discovered that I require 3 x 25mcg Cynomel (Liotirinina - T3) a day to feel well. My feet are now warmish rather than blocks of ice.
Downside is that I have only 100 x T3 left, so will be finished in a month and it akes a month to receive new order, so now is the time to order more.
Would be great if there are better deals out there from a reliable source.