i live in a flat and also on a water meter and use around 1000-1200L a week.my tap tds is usually around 35 so just a DI (i use a monster 25L vessel)and lasts me around 6 months before needing changing.
i have a hose from my bath tap,down my stairs to 10-12 barrels in the back of van.it takes me on average 40-50 mins in the evening after work to fill the barrels.
it works well for me and i bring my 50L P/F TROLLEY in every night for charging and DI and poles/extension hose if its sub zero at night with a thick duvet over my barrels.
its the best thing ive done for my business and im really getting into it after 10 months WFP!

itll be costly for you with such a high tds from your tap to go DI only but there again with a ro you ll have loads of waste water and itll take you ages to purify enough for work so your water bills would be sky high!!

dont really know what the answer is unless you go di only and just wfp the tops.that would keep your resin usage down a bit(and use twin DI s IN TANDEM)
dazmond