A BP depot is next to the servo i use (I know my fuel will be fresh all teh time ) and I decided to walk in and have a chat to the rep....
He says the three major petrol manufacturers that make 98RON fuels (BP, Shell and Mobil) each make their own 98RON fuels and dont share it between themselves. BP make Ultimate in Perth and Brisbane. And he said that they all share 95RON (and below)fuels between each other, so BP unleaded might be found at a Shell or Mobil bouser. And BP is considering dropping standard Unleaded in the future.
BP make racing fuels (AvGas and Methanol) as well but they all contain lead and will kill your O2 sensor.
He also said that he heard of a company in Sydney called VP Wholesale (?I think?) that makes (or is in the process of making) a street legal 100RON unleaded and selling it in drums.