Hi Tracey,
I imagine that data would be extremely difficult to accurately collect. Not all window cleaners are members of the NFMW&GC. Even for members, the fed would have to send them questionaires to collect such data.
The federation is non-profit making body, and I doubt it would be willing to send questionaires to its members for this reason, and using resources to help a private company for little benefit to its members might be considered irresponsible.
However, I have an idea that may help you - why don't you set up a web page with an online form. Direct us forum members to it by means of a post and we could fill it in online. I'm not sure how difficult that would be for you to set up, but you probably know more about this than me.
Personally I wouldnt mind spending a few minutes filling in an online form. I'm sure other members wouldnt mind too. If you need any help choosing your questions, just ask. (some of your proposed questions are a little bit inappropriate - "do they use just water" is a bit like saying "what time is it- YES or NO?" there are many different methods depending on the job)
Silly