Tim,
Click on
http://www.titanlabs.net/gg3.htm for all the details you need. GG3 is for soft water and GG4 for hard water areas.
If you're eventually going to be WFPing, it's much better to clean the existing windows with GG3/4 as they leave no residue. Much of the kerfuffle in the first job or two is rinsing out the F***y L****d residue.
http://www.cleanitup.co.uk/cgi-bin/yabb/YaBB.pl?board=Equipment;action=display;num=1088437075;start=3#3 should keep you occupied for a while. If you click on the search button at the top of the page and key in what you're looking for, you'll normally get quite a few results.
All the best with the WFP - key that into the search facility too and see what comes up!