I would agree with what Darran says. I started with a trolley sytem, and you will spend as much time changing barrells ,as you will actually cleaning..
The other thing to consider is the battery. Without it conn3cted to a smart charger in the van, it will,lse power very quicklly. I have a 210litre upright tank,which lasts me all day most of the time. You could get a lay flat tamk, which would be easier to remove, innthe sense of handling.