The system is outstanding I have the same , I'd say the system Just on its own is worth £1500 .
I had mine in a 260swb tranny and I got pulled in at the WEIGHBRIDGE 2 months a go and I was 300 kg over - had to dump water , acted dumb and didn't get fined .
650 litre water
Battery , filters , RO ,commercial pump , shurflow , 2x 100 m hose reels , poles , me 80kg , diesel 40kg , extras
Roof rack 50kg
Ladders 30kg
That van , like mine is illegal -FACT , been there and done it .
Hence I transferred mine into a 57 plate Transit van T300
The above can be ok with 350 to 400 litres of water .
If I was the seller I'd just fit it into my newer van -I did
It's a great buy at that price but limit the Water filling to 400 litres I'd say