Looks like I have left it too long to post some pictures. I wanted to show how I have mulched the garden using chunky mulch as recommended on this forum by Ekka and Boa. The trees are doing much better now, helped by some useful rain we have had since I bought in a truck load of water and applied it to the garden.
Another benefit of the mulching and watering is that the palms have been dropping a lot fewer leaves, so there is less cleaning up to do. I will try posting the pictures on a new thread.