I fully support this type of thought. I tend to frequent farmer's market and only buy at Woolworth's items that I know are cheaper than what is already availed at my local IGA. I also ONLY buy petrol at BP and have not frequented a Caltex or Shell in over 5 years.
As an example, the milk that I buy is direct from the farmer, unhomogenised and unpasteurised (bath milk) as I use the milk to make my own cheese and yoghurt. If not that than Harvey Milk over Pura.
I too am disgusted at the power that Woolworths and Coles have and will not support a oligolpoly at the detriment of Australian producers.
Please view the below image an an example of the monopolies in the food industries and companies to avoid. I place Nestle next to Monsanto as the epitome of evil in the global food industry.
Here also is a link of ALL the water brands that Nestle own:
Nestle Water
Here is also a link to what the CEO of Nestle thinks about water. He effectively states it an underpriced resource and if you can't afford its true price so be it.
Water is not a right and should be privatised : Nestle CEO