Some c%&p diesel...

I'd be going straight back to woolies and sticking it up them as soon as it happened and also get a sample from your vehicle tank and get it analysed, big companies will come to the party on repairs, I know a fella with an old Peugot diesel that had the engine rebuilt due to a crook load of fuel.

In this particular instance, salt water is entering the vessel and contaminating the fuel. Common sense would determine that during periods of peak tides ( I think the moon has an influence here) the sea lavel is above that of the tanks. So a likely scenario is your common garden variety servo monster at a pre-determined time, is required to fullfill one of their job description duty statement roles, ie. "dip the tanks" in the process of performing this task, a small quantity of salt water manages to enter through the neck of the main vessel and over an extended period of time this increases to a level that has/can and will cause internal combustion motors to have a fatal event and cease to function in it's primary role.
Subsequent complaints to the parent company result in checks an analysis of the suspect fuels. To date there is no problem with the fuels, so must be another source or another component of the motor vehicle at fault. The analysis has been conducted by the fuel companies own labs! (HELLO)
In reality this is on a larger scale than taking a urine sample from an international athlete and finding a positive result. We are up against multi nationals here, and they in no way, shape or form are going to be dictated to by us the consumer, that is, without a fight. I am not familiar with your bank account details but I definately do not have a spare billion set aside for adhoc legal expenses. Maybe thats why we pay to be members of our state motoring organisations.
Speaking for those motorist that are victims of this particular fuel outlet and its parent company, the placement of a "CLOSED FOR REDEVELOPMENT" sign displayed at its entrance .