I bought the TMC V2 Pure Advanced unit about two months ago from the local Maidenhead Aquatics had it for a good price, and I think it is good value.
Like yourself I am not on the meter, I now have 600 litres stored and just top up the tanks as i use it, I get a TDS reading of between 1-3 depending on the quality of water going through it each day, its surprising how the quality changes by the hour. It has an inbuilt TDS meter which shows the quality of water coming in and going out, and also a flush valve. Like Stu said it does not make the amount of RO water as stated in the literature. I have it installed in my shed and have put a long length of waste pipe on it and I just move the pipe around the garden and leave it to water the plants.
I purchased mine as I had a bacteria problem in my water butts and considering I was stocking 2200 Litres in butts I did not know which one was the problem, so now I do not have to worry, I use around 80/100 litres every couple of days or on hot days I can use that a day.
I also grow a lot of Disa orchids with the Carnivorous plants hence why so much water is used.
Hope this helps.