How tall are you bonjoy? I had ( ) a citroen relay and its about 5'10" wide inside - meant I could build the bed sideways which saves a load of space and faff with folding mechanisms etc.
Maybe a camper version of those sub-transit style mini-vans
in Scotland just find a spot off the roadside ,never been asked to move on,
the device needed is called a split charge relay, simple to wire and available from halfords etc. Ive got a solar trickle charger that plugs into your cig lighter and will keep the battery topped up. They're cheap too. Might be an idea to get a leisure battery that is capable of jumping your starter battery, that way you can jump yourself if your in the middle of nowhere, I know its not great for the leisure battery but now and again wont be too bad.