To be clear, when you say "bottle conditioning" do you mean natural carbonation in the bottle? Or do you mean aging the beer in the bottle?
If the beer's already carbonated and you just want to age it, temperature is much less important. But I wouldn't put them anywhere with huge temperature swings, or where they might freeze. To be honest a garden shed sounds like a horrible place to cellar beer. Do you have a basement? If not, a dark closet or cabinet works well. Try to keep the temperature consistent and cool (50-60 deg) if you can.