After doing the Bunnings run and being offered deck cleaner with a mix of oxalic acid and hydrochloric in liquid form then told no we don't have it in flakes

So its not just me! Thanks for the info. I will pick some up next time I am there. What seems an easy trip to Bunnings can turn into a frustrating adventure some times.  I was searching for Ranex for an hour as it was impossible to track down a staff member to help. Finally found it in the metal rust conversion/spray can area in the paint section.