Matt
You are not compairing like for like with your pricing
You say you bought a pump for £40.00 obviously this isnt one designed by shurflo flojet or any other manufacturer specifically for window cleaning and as such you would invalidate the warranty as the manufacturers do not warranty their standard pumps for window cleaning usage due to the wear and tear involved in this task.
Secoundly you advocate the use of either 2nd hand car battery or a new car battery as you will be well aware these are not designed for operating pumps as the plates are thinner and not designed to be used all day just for short bursts of high power to turn the flywheel, so are much cheaper to purchasse than deep cycle bateries.
Are you suggesting that wfp suppliers should be using the above componants mearly to save costs.
no glyn, i am giving different options, sharing a bit of info to others, giving others the knowledge that you can do it a different way ( you know, just as i did all them years ago )
my pump is a small pump, its not branded, but 3 years on, have i been lucky, i guess i have, though to be honest, we all know some1 who has had a flojet / shureflow that have failed after 15 months
i know about leisure batteries, ive owned 1 ( i am on many campervan / motorhome forums, where they are essential ) a cheap car battery for 30 quid will last the same time as the small batteries that are put in trolleys ( higher amp, thus not so discharged during a long day, as we know if you hammer a battery and it drops below a certain charge, it doesnt do the life of the battery much good )
for me, a 2nd hand car battery which lasts me 6 - 12 months for free works very well, when it dies, it gets changed ( now if you dont fancy asking at your local garage, just buy a new battery for 30 quid ) i like the idea of using 2nd had batteries, as its far greener, its recycling as it is s.posed to be

its really not about the money ( though i am sure the knocker will say " your too much of a cheapskate to spend 30 quid ) i recycle my plastic, my cardboard and glass and metal, so why should i send a battery to the tip that will be shipped to india to be stripped by some poor scavenger child ? ? ? ?
this will be your Q for the line, well if wfp suppliers dont make money, they will not be able to spend money on
R&D, thus DIY'er will have nothing to copy