I bought a Kangoo Maxi earlier this year which has a full bulkhead. I thought I’d only sleep in it a few times a year so thought I leave it with just the ply lining to start with, and see how I got on (having heard everyone harping on about condensation). I’ve already used it way more than I was expecting (including a week and a bit in Scotland)The coldest I slept in it was 4*C and it’s been great. A couple of sections of the roof have a light misting in the mornings, but not enough for droplets too form.
It’s my only vehicle, so I mainly have it empty or just have my bike in it and a box with my riding stuff. I’ve always preferred basic cars, and with the bulkhead, the van is at least as quiet as my last car (a C1!). Not having built in beds and stuff means I can still use it as a van if needed.
I use a fisherman’s bed chair thing to sleep on – it’s very comfortable and I can shove a couple of storage boxes underneath when going away.
I think if you’re going to use your van like this, you won’t need much insulation. A mate who has a much nicer, insulated and carpeted van (without a bulkhead), says all the carpet traps the moisture from wet bike/rider/stuff, so in the winter the van steams up all the time.
PS Vans are great – I should have got one years ago.