In reply to Dottie:
I know you say you want a "fixed bed" but don't forget the long nights! I.e. if you're genuinely just planning on using it for sleeping then fine, but consider even a simple slat/box bed that converts into some form of sofa. Much nicer when you're back from the hill.
To be honest, I don't get the whole idea. If you just want somewhere warm to sleep, get a good sleeping back and Skoda Octavia - most of my mates have similar and sleep in those all the time. The first time you arrive back to the van in hoolie and you have to change outside, or on top of your bed (getting it wet and mucky), then go back outside with your trangia to slowly warming up your dinner while getting colder and wetter again...you'll be wishing you'd even built a micro-kitchen and a small seat area.
However, if you are fixed on a van, the other people's suggestions of a sealed, lined, waterproof drying room with a heater outlet, floor drain and decent ventilation will probably be required.
We have a self converted T4 (bought in the Netherlands to avoid scene tax) with no heating and I wouldn't expect damp clothes to be dry second day on. The floor gets wet and stays wet until we dry it at home with towels, and the cups of tea are very nice
Where are you based, you can have a wee look round sometime if you want?
