prefabricated 'Pole wash' or Water fed pole reach and wash systems can vary greatly in price from around £800-£20,000
so it depends exactly what you want. Water capacity, number of users, whether you are looking for residential or commercial customers, how many systems, size of your van/s, quantity of work you are aiming to use it for, what water supply tds you have high(400) low (50) so whether you need a ro system or just di. Lots of factors in choosing.
There are several companies offering systems, all you have to do is search in google water fed pole system/reach & wash system. Though when you specify your choices, more members will be able to offer their opinion for your needs.