Buffer tank is important, makes jobs easier if you can continuously work. You can get pop up water holding tanks. If your short of space maybe something like that will be useful to you. If you get a 21litre machine your looking at around 80kg in weight, you would be better of with a trailer or van. It's too heavy to lift into your Ute. I go the gym have done for years but I wouldn't want to be lifting a pressure washer that far of the ground.
No I don't want to be lifting it off the ground either. The problem for me is the added expense of a trailer and storing it. I would have to pay for storage somewhere when the pressure washer is not in use. So the added expenses are £1500 for a trailer, £1500 for pressure washer + £50 per month storage fees. And no guarantee of work either!
If you were in my position would you bother?
ps I do appreciate all your help.