Okay I'm here...we live in a hard water area and have installed a Culligan Water Genie, this is connected to the inlet flow into house under the kitchen sink. We have also has a separate filter system for the drinking water.
The water genie is brilliant and I must admit to leaving on when I wash the car as it makes a world of difference as it deson't streak and also the water marks instead of marking the car can now be removed easily.
They cost about a £1k all in with fitting etc but shop around as some companies will do you a good deal on them, the only thing you need to factor in is the salt about 1 bag every couple of months and an annual service plus the new filter for the drinking water system.
http://www.wrekinwatersofteners.co.uk/wrekinwatersofteners/final.asp?id=95This is a link to the company that supplied, fitted and look after ours....very helpful, ask for Graham if you call for any advice...tell Sonia and Wayne gave you the details...
Sorry for not much detail as I'm on a neighbours PC due to mine dying.....