My builder uses Houzz Pro to plan the timeline and give detailed estimates and daily updates with photos of progress, and provide invoices at pre-agreed key points in the build. This made the whole experience much more efficient and stress-free.
We used 6" thick bluestone, thermal cut mantels with a Winter Park MasterCut stone veneer. We purchased the stone from Charles Luck Stone Center here in Raleigh, NC. I'm not sure about availability in Australia, but a local stone yard should be able to let you know.
Landvision Designs, Inc.