A cheap quick DIY alternative to your problem would be to simply place the cylinder in a bucket of water. As long as the water does not freeze up during your winter months it should be sufficient to solve your problem..
Interesting thought, but have you tried to lift a full 45litre bottle of LPG? My gas man has to do a shuffle or five to get it onto a ledge only 200mm above ground level - and that's after I did him a favour by taking out a wall that was 600mm high. And the problem only occurs in Winter when any water is going to rapidly cool.

