Hi, Woodsman, bugger them with their silly jokes
I can confirm the thing with the ENGEL box, probably best box around... Although: I'm seriously considering to build my own, parts can be found
here — it works out cheaper, and you can make it any size (w/in limits) you like...
Heaters and water heating: very complex issue, maybe first set up a profile of your estimated usage...
No, I don't want to be a "pain in the butt", but there are a number of heaters on the market which use the water circuit of your engine cooling system to (pre-)heat your camper cabin and shower water; they are of no use to you if you don't want to drive frequently (eg use your truck more as a home than a travel vehicle...).
Will you have access to 230 Volt power (at least frequently)? Solar panels don't work that well with a foot of snow on them, most heaters rely on power for either pump or fan, or both...
Do you want to spend an entire winter in your vehicle/camper? Then it might be worthwhile to consider under floor heating with water pipes laid into your floor (seriously!) — I'd say it's me more cozy and not much more expensive to run, but the investment will be higher.
You see: a profile of your heating requirements would be a good starting point; then you can ask more precise questions, or search this forum and
WoMobox.
A wood heater is not such an uncommon sight in campers; different countries have different regulations (as far as I read even different states w/in Germany).
Also: budget limitations are a good thing to make public — the "sky is the limit" will get you a lot of silly answers...
Best buy a ready-built luxury camper for a sheikh in Saudi Arabia or Oman - the like of UNIKAT come to mind.
Stoves for cooking: diesel stoves are available, but they heat very slowly, and (despite what everybody claims) still smell a bit. They also have issues with altitude. Most common option would be a propane cooker; unfortunately the ones commonly used in RVs (and carrying proper certifications) usually have low output-burners = no good to cook things in a wok for example. If you search in boating supplies you can find nice gas stoves with minimum 3kW burners (RV cookers have at best 1.5kW - not straight forward to actually find this information), but in Germany it can become difficult to get approval for these (it has been done, though), GB might be different (in the unified EU - LOL).
Again: SVB (link above) could be a starting point to look for such stoves, then you can compare with offerings in GB.
I hope this helped a bit...
Final question: do you know the Silkroute club in England? Many knowledgable people there (and some airheads, like everywhere) — might be very helpful to you with more GB-relevant searches and/or questions:
http://groups.yahoo.com/group/silkrouteclub
Thumbs up from down under!