Over on RRS.co.uk there is a group purchase of this kit to aid car washing if any body is interested. Here is the link
http://www.rrsport.co.uk/forum/topic6450.html

This system uses de-ionised tap water (same as you get out of a home dehumidifier) to give you a blemish/ water drop free finish to your car after washing. Anybody who has used the "Flash" carwash system will have used a similar device in the rinsing section of it. This one fits on to your hose at the tap via Hoselock type fittings. It especially good on dark coloured cars where scale deposits from ordinary tapwater drying onto the car can ruin a good day's carwashing! How can carbon have a footprint, it has no feet?
Now driving - RRE Coupe Dynamic Lux Auto with Plus pack, Fuji White, Ebony, SD4 with tow pack
Gone - 2010MY FFRR TDv8 Stornoway and Ivory, Privacy - the pace of a TDv8 RRS, the incomparable grace of a Range Rover
Gone but will be missed- RRS Tdv8 HSE Stornoway Grey with Ebony Leather
Gone (only a little missed) RRS Tdv6 2.7SE Giverny Green/Aspen
Defender 90 County HT in Epsom Green

Nice one Tim, I'll take a look. In the heat we had in April I couldn't get round the car quick enough with the chamois to get the water off, and as you say, water marks where found wherever I was too slow......so took to washing the motor early am or late pm whilst the sun was at its lowest.