Knobby,
I believe there are places in the world where this is very relevant. In very cold conditions, when doing an instrument approach, it may be necessary to adjust your decision height or minimum descent height to take the temperature into account. Otherwise your indicated 200' can become considerably less.
It's been a little while since I learnt this, but if I remember correctly it's 4% for every 10 degrees below ISA - so if the outside temperature at sea-level is -35, you need to take 20% off your indicated altutude. That means you're at 160', not your indicated 200'. Which could make the difference between making an early impact with the ground or not. (I'm sure someone will correct me if I've remembered the forumula incorrectly.)
However, I will grant you that although some airlines who fly into cold airports include this in their standard operating procedures, it's not very relevant to the average British PPL
FFF
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