What's your tds? If it's particularly low then you might not need an ro. if you do need an ro and have the space then for fifty quid more you can use that one and set up a 1000l static system in your garage. Pump your pure to the van when needed. Have water producing whilst your at work then if you want.
I wouldn't advise an ro in the van if you can avoid it.
thanks for all the reply's
my original idea was to have the R/O in the garage but i got a 1000 ltr ibc and there's just not enough room in there so i'm going back to the idea of van mounted also i am living in rented accommodation so thinking long term just put it in the van to start with.
i know people are advising against this but dew to room i think i have no choice.
as for tds i dont know how high it is but i know it is a hard water area so i will need R/O unit