I have used a van, but then had the cost of running two vehicles. I have been using a trailer towed by my Passat for the last 4 years. I altered the trailer to suit my needs. It has a ramp for the trolley and carries 14 containers if working with my lad, less if working alone. I am still using the same DIY 50ltr trolley system I desinged and made about 10 years ago, I am on my second varistream but the same original Surflo pump. The hose reel on the trolley holds 40 meters of micro bore [ I had to replace the original] so know worries dragging a trolley round the backs. My wife fills containers from the DI only system, twin vessels and a tap water TDS reading of 47 ppm
I couldn't do a lot of my round with a van mount without using 200 meters of hose.
Of course I could just put a tank in the trailer instead of 25 ltr containers, but with a mostly highly compact round I much prefer to work with the trolley. Even though it's all aluminium construction I can still stand on it to unlock back gates.