Simon,
Call Dylan from Blue Mountains Adventure Company (
http://www.bmac.com.au/). He owns two of the four commercial canyoning operators in the mountains (he also runs climbing, abseiling, bushwalking tours etc). He is also on the local tourism board, the outdoor adventure council, and generally seems to know every guide in the Blue Mountains. He'll either be able to help you, or will put you in touch with someone good. Also for disclosure, I went to high school with him, but I only reconnected in recent years due to outdoor pursuits.
T2