Oh no - I went through one mowing the lawn last week - thought it was a caterpillar but had no idea what sort of beast it would turn into (at least, before it became two parts).
The caterpillars can get pretty big and the moths themselves will have a wingspan of about 70mm. Very pretty things.
I think their main foods are fuchsias, brambles and those sticky weeds that kids stick to each others' backs.