Hi, yes we have the twin tub. It actually works very well. It only does a small load at a time, but the clothes come out clean, and the spin drier is very effective.
It does however use quite a bit of water, a full load takes about 17litres to wash, and then you need at least 2 rinses, so 50 litres to bring and then take away, and of course it needs to be warm/hot.
We used hot from the van and added cold from the Aquaroll using our portable pump. To drain we piped it direct to the wastemaster. We sat the machine on a small table.
On a serviced pitch it is easy. If you are close to the site facilities you could fetch hot water. I found that I could do 2 washes in the same water, just topping up with some hot in between, then doing all the rinsing.
I found it could wash several T shirts in a go, even a pair of jeans or a bath towel or a double bed sheet, and for underwear it is ideal. A double duvet cover is too big though.
When we were away for 2 months recently I found, with 2 of us, I could keep on top of the washing doing 2 loads (one whites, one coloureds) every 4 or 5 days. When changing the bedding I used the site machine and added the towels or whatever to make a full load.
Although not very heavy, it does take up quite a bit of space in the car. You could carry it in the van if weight is not a problem.