radical thought this, but what about a hotel room? You don't need to drive to your destination at 55mph getting crappy mpg. You can actually enjoy the drive down & not hold anyone up in the process!
You don't have to make your bed, empty your own shite, cook your own dinner, clean up after your self.
Save yourself a bunch of cash too 
we dont all get paid lots of cash for sitting around watching telly and eating ice creams 
Exactly why you should use hotels, lot cheaper than a burger van 
average night stay in hotel lets say £50.you can get a site for £10 a night with leccy and shower if you shop around and you still have to drive there be it with a van on the back or going to the hotel so the petrol more than favors in the cost of taking your own home rather than paying for a hotel and if it comes to kipping in a tent or having a proper bed and a toilet and a fridge and warm water and a shower and a kettle and a toaster and a oven and a grill and lights and a wardrobe and storage space and bbq and gas fire and leccy fire and music and telly and dvds and satellite telly and digital telly and the list goes on....rest my case
There in you sink your own case....you have so much costs up front...
Van Purchase? Anything from a grand to 20 grand. Buying security bolt ones, wheel locks ect, going to wash it, check on it every few months. I don't check my hotel rooms are ok few weeks later
Depreciation, who knows? Least few hundred a year!
Site fees £80 for a week?
Storage? £300 a year? Is it near you, suspect you have to drive at least half our to get to where ever you keep it
Insurance? £200?
Maintenance / Tyres / Service - £150?
So before you take the damn thing anywhere you will have spend a nights worth of accommodation minimum, easily two!
Fuel 50% worse consumption. London to Lakes, your looking at spending £120 odd in fuel, assuming 15mpg, compared to £60 at 30mpg, so again, another night there.
Sorry but dragging a plastic box at snails pace, then sitting on plastic furniture, getting your own water, emptying your own poo is not my idea of a holiday!
I had a week in Portugal, Camping trip to Cornwall & week on the Isle of Man on my motorbike, for less than the running costs of a Van, before you've even taken it anywhere!