It could have the best window cleaning gear in the world in it but if the van is not reliable what good is that?Concentrate on getting a half decent van first and you can diy a system yourself without too much bother. 
I couldn't agree more.
Someone who hasn't got the mileage clearly is trying to hide something. I wouldn't be surprised to find it was 150k.
I have also neva been convinced that a flat tank is ideal, certainly not in a Berlingo. I don't like everything that is ontop of a flimsy base over the tank.
There is also a slim chance that the Berlingo is one of the first editions that didn't have power steering on the 600LX although it was standard on the 800LX. No power steering is a big disadvantage.
The pump and Varistream are 'new' - the Varistream is the latest model, but I don't see a pump strainer. I wouldn't want his tank (I prefer upright), don't want any of his poles, and I prefer to use minibore hose as it has a slighty bigger inside diamt.
I would also opt for a Berlingo with a rear side loading door as well. I would also need to have a factory fitted steel lower bulkhead and upper mesh bulkhead, but would find a scrap one at a reasonable price.
So actually, the van is worth £200.00 to me, £80.00 for the pump and Varistream and £120.00 for the van as scrap. Might be some tax I could cash in on once the van was registered in my name.