Andy & LWC
I also have a Sprinter XLWB that we bought from a chap last year. This is set up as a camper as well with the work area in the back. That one has a 1000litre system in it, Sleep 4 but would be tight. This van has a safari room on the side of it - basically a fixed awning that winds out and you add the sides onto it. This van is set up solely for pressure washing and we carry no water off site.
They are not roomy but I have tried to make them as comfortable as possible. The Movano has a 400 litre tank in it, all the bed and cushions are being done this week and a large tent will be driven up to for the Movano as additional living area.
Ultimately tring to get away from dragging a caravan through places like Marble Arch - London on a Friday lunchtime - as happened last Friday
Rob