Hi Seanysean
Before you collect the van just ask the hirers to make sure that the batteries are fully charged.
We wildcamped around Scotland a couple of years ago, our van had an 85amp battery and we had no problems. The bigger the size of TV the more power it will take, we used an inverter (a 300 amp can be used with anything with ordinary plug) to charge the laptop while driving and also if needing to charge it over night. Also charged camera batteries while driving.
We found we didn't really watch TV as there was always something to see in the evenings, so apart from the news and weather it sat in a cupboard.
We found lots of places to camp, on beaches ( above the tide line) in car parks and forestry commission lands. Even sat with the rangers some evenings while they told us about interesting things in their areas.
A lot of the picnic areas have got water taps that you can use to fill tanks, be carefull where you empty your waste tanks though, remember other people would like to enjoy the area without your smelly washing up water and worse around their ankles.
We did pull into a couple of sites just to empty the loo and fill with water on a few occasions, there will be a charge for this as camp sites with ceptic tanks will have to pay to have them emptied and as a non camper with them it is only fair. Not bad for about ÂŁ5 every few days though.
Ask Locals if they know anywhere you can park up overnight, we were directed to some lovely places.
We also printed off details from this site before we went.
http://rutgerbooy.nl/Wildcamping.htm
We found it very helpfull.
Wildcamping motto corny but apt: Take nothing but memories and leave nothing but footprints.
Park with your line of escape easy, ie don't drive nose first into a dead end in case you have to move in a hurry. Don't leave chairs tables and other things outside the van at night. My rule of thumb is if I don't feel safe we find somewhere else.
Have a fantastic holiday
Tina