In reply to CharlieMack:
Ive owned a T4 and now have a scudo. My top tips are;
Self Build Motor Caravan Club website for endless self build ideas and forums.
Adrian Flux for insurance. They cover all kinds of oddities and arent expensive. If you fit any kind of burner (hob or stove), or admit to lighting fires within your vehicle, ordinary insurance will not cover you.
Ive never gone high top since its limits what car parks you can get into. Most in the UK are 2.1m, though some multi-storeys are scarily tight at that. Im short too, and never missed the full standing up experience, though I never spent more than a week in the van.
Take a small tent. If using campsites, pitch the tent and throw all your crap in it. Assuming the van isnt massive you *should* only be charged for one vehicle and one tent (ie same as ordinary camping). The van is then a luxurious sleeping den, with less stuff rolling around in the back when you are zooming to the crag, and without the smell of festering clothes and damp cheese etc. It also saves you a pitch at the campsite.
Oh, one last one, I got ex-MOD foam mattresses for the back and they are FAB. Cant for life of me remember the website, but they shifted all kinds of ex military stuff mainly from barracks, lots of tables and desks as I recall.
Good luck and have a good time!