the size of the partitions was dictated by the windows, this is something to take into account when deciding on a base vehicle,my second project "RUBYCON" is based on a van, so the internal partitions are factored around the fittings.
So, the start, once the layout of the van had been decided, it's time to insulate, on a minibus / crewbus only the panels below the windows can be insulated along with the doors and roof, some might say "but whats the point, the windows are not double glazed",but when curtains are fitted, it does make a difference.
The choice of insulation is simple, rockwool loft insulation, expanded polystyrene or foam. the last two are messy so i used loft insulation.itchy but cheap. for the roof i chose a foil bubble wrap sandwich used for insulating behind radiators, i also used it for the thin "window" panels in the back doors.
My larger van based camper "Rubycon"will also have rockwool and foil insulation.
floor insulation is a matter of choice, in Ruby i fitted carpet over the top of the standard wooden floor, as there is a small air gap under the floor and with the carpet ontop, cold has not been an issue, With Rubycon, i will fit parket flooring underlay , then the wooden floor and possibly cork tiles on top, this will provide plenty of insulation.
Many converters advocate fitting the wiring before the side panels go on, i choose to use available channels such as where the van sides meet the roof, this allows easy access and the opportunity to modify at a later date.
However, wiring for ceiling fitted lights will need fitting before the roof panels go up.
In Ruby i used 12v flourescent lighting, but Rubycon will be fitted with led lighting throughout.
led's use less power than normal or flourescent lights, handy if you rely on batteries for power.
Both of my vans are battery only as i dont intend using too many campsites for 240v hook up.
Water and waste,
for Ruby, i used a 25ltr water container fitted between the fridge and cupboard, this was a tenner or so from ebay, it feeds a whale hand pump tap also from ebay.the sink is a converted serving container from a canteen, it is fitted with a plug and drains via a pipe through the floor.
In Rubycon, i have a 90ltr water tank that will feed via an electric pump all the taps and water heater, (all from ebay).grey water will drain into a tank fitted externally under the floor, and emptied through a tap and pipe.
The thetford toilet has its own waste tank but will be flushed from a small internally fitted tank.