1000 ltr IBC..well darn it
You must almost empty it every day Andy.
I WAS going to suggest 2 x 300 GPD units (pumped) because these would definately be the most economical for you to run in terms of DI use and waste water.. 1 to 1 on a pumped ROand no softener as well but ho hum to that idea!!
A decent pumped 300 will give you 800 to 1000+litres per 24 hrs so if you had enough storage you would be fine.
I would think a good 40 inch set up would be your best bet when you move.
Andrew