James,
I use the clarke pump CBM240E with just garden hose that you can buy anywhere B&Q and such, its never collapsed my hose at all lol.
If you dont want to spend as much as £300 you can get the CBM pump without the electronic control but i think its better with it as it will switch the pump off if something happens like.. someone switches the tap off thinking whats that doing on etc stopping the pump from ru nning dry.
http://www.machinemart.co.uk/shop/product/details/cbm240-1in-multi-stage-water-pump its only about 200 pound without the electronic control.
People have said on here its not noisey ... i think it is really for what it is mines set up in my garage even with the door shut i can just about hear it outside but it is in a boxed unit, i will try take some photo's later if i can.
My tds used to be about 30-31 before using the pump, i dont have a lot of water flow from my tap and even still its not running in ideal conditions it brings my tds down from 30 - around 17-20 depending on the time of the year, thats the lowest i could get it to. I dont how much yours will come down as its too hard to tell.
so window cleaning warehouse have said they have a pump for £1100 -- are they joking? thats outrageous!