My static tank is sat outside on the floor, as is the R/O..never had a problem in over 3 years...no...I lie...had one day a couple of years ago where I could not fill van tank as weather was so cold the water in the transfer hose froze solid!

...though that wouldn't have made a difference for me even if it had been in the shed...transfer hose is 50m long and has to lay outside.
These IBC tanks come with their own frame and base anyway, so will sit happily on the floor.
Lagging your R/O is sensible though, and very easy to do.
If you are going to get a van, get something transit size, I have a Nissan Primastar, and a 650l tank, and even on very, very busy days I no longer run out of water, but even that will depend on the kind of flowrate you have, even with a 1000l tank, one man could run out of water in a single day if the flowrate is high enough.
With a tank and R/O in the van, for fast fill you have to have an expensive R/O, this is fine of course if you have money to spare, but you also need to connect up every night to refill, a static system at home is easier of course, but you do lose that ability to top up as you go along.
I fitted my own tank & cage, was easy enough, but for piece of mind it is better to let someone who knows what they are doing to fit it for you...all depends on the depth of your pocket and your own DIY skills.
Keep asking questions on here though

Ian