Gary - you've probably worked this out for yourself, but to avoid a meter giving a "too cold" error, then if it's been left somewhere cold (in my case, more likely in a rucksack or tent on the fells) then it and the strips needs to be warmed up before trying to use - between a T shirt and midlayer in the armpit is ideal - not right next to skin, as that's very cold and uncomfortable! Leaving a meter in a car isn't a good idea, as on sunny days it can get too hot.
With some meters eg Optium Xceed, an error message appears as soon as you put a strip into a too cold meter, but before you add blood, so no strip is wasted.