4.2 pence per litre is very expensive.
I currently produce my own water (using a standard HF5 4040 RO) at about 0.8pence per litre. (Includes metered water, sewage charge, prefilters, resin and replacement RO every 5 years)
I use about 700 litres per day, so my own water costs me about £28 per week.
Usung Spotless would cost an 700 x 5 x 0.042 = £147.
That’s an extra £119 per week, or over £500 per month more.
I just have no clue why anyone would do it!
And that ignores the more important issue of being dependent on someone else for your water, which I will NEVER be.