Well, I mean, all that tripe about paying £20000 for 'development', when it's already been done.
Sod it, all I need to know is how much a pw consumes water-wise and weight it up.
Thinking a bit more about it, you could have one tank of nasty high TDS water for the main clean, and then flick a switch to use the pure stuff for rinsing. Gonna need a LWB Transit I expect, and two IBCs, or one biggun for the high TDS stuff and a 500l one for the pure.