Bluesmoke,
I know a lot of shooters in this area (USA, Florida) that used pillow ticking for patching were finding difficulty getting it in 100% cotton. And as most of it now comes from China, the quality varies greatly between batches. I've used denim, drill and even light canvas, all available in 100% cotton, for years. I usually buy a few yards at a time and stash it away because it doesn't go bad and I don't have to worry about locating it for sale for some time. I don't know what the fabric stores in Australia carry, but you might think about trying some of that if available.
Mole Eyes