Thank you for the photo (which can be found on this site under photos) I think you prognosis is correct and the damage is Tortrix Moth caterpillar. We have found very little in the way of pests on the trees here on the nursery but Tortrix seems to have a particular penchant for Wollemi Pine. Consider using Tortrix Moth Trap; these use a pheromone to catch the male moth. Moths fly during the day, in early summer and again in early Autumn. In a heated greenhouse or conservatory they may be active all year round. The trap should be suspended above the plants which are at risk. Check the trap frequently. As soon as one moth is caught, spray the plants with Bio Sprayday Greenfly Killer Plus or Liquid Derris Plus.(Always follow the recommendations on the packaging). Spray again every 2-3 weeks while moths continue to be caught. The easiest method of control is to pick off affected leaves and burn them.