Hi,
Thanks for all the replies, good food for thought.
However, a word of caution if using the salt solution as above - Rock Salt for instance is only good to -6 degrees, depending on the strength of your salt solution it may initially cause a thaw, but may then well freeze agian as the temp drops - leaving the water you sprayed on as a lovely slippery layer of ice.
Also Salt is an excellent weedkiller - so be careful where you apply it.
Thanks