I've seen some long tall thin oil tanks that would go up against a wall nice and can be used to store water, they might fit through the gap.
If you are filling straight to the van, I take it you have an ro in the van, can't you transfer that to the static.
As for transfer pumps, I have a 170L/min sub pump, it works well. It does depend on the tank you have though as to go for a sub or external pump. A sub pump will be cheaper for the output you get.
Simon.