Golden 6, I believe your problem is twofold. Firstly you need to enrich the soil in terms of organic materials for the worms to live on. I have found that combining sheep, horse and cow manure worked well. Sheep and cow manure I suggest you buy from a garden centre as it is convenient. I have also found that cow manure from the paddock resulted in weed infestations even though I ran it though a garden mulcher. Having horses I simply went smelt less and to the stables but made sure I took the older manure as it smelt less and attracted less flies. I used more horse manure than the others as it was handy and free. I am sure any stable would willingly let you have some. I put it onto the surface of the soil (in this case the vegie patch) at about a depth of 15-20 cm. I would add sheep and cow manure once the plants had become established. I aslo found that fish emulsion and seaweed concentrate applied onto the plants fornightly worked wonders.
In summer I did mulch with STRAW or PEA HAY heavily and could not believe the difference this made to the soil temperature and its abilty to retain water. THis I believe is the secret to keeping your worms in the garden as they move up and down in search of food and to get away from the hot conditions.
Chemical solutions may provide quick initial results but long term they are best avoided. The down turn is that the compost, manures and mulches need to be continually replenished, but that is part of the joy of gardening.
Hope this has been of some assistance.
PS Give your local library a visit they should have a heap of info - Gardening Australia mags. I think it was Ester Dean who wrote a book many years ago which from memory was called No dig Gardening or something similar.
