I think what we could expect to see, is some customers buying the water and cheap poles, then cancelling their window cleaner.
A year later, phone rings ‘urm, can I have you back?’
If Tesco did sell pure water, and a pole system etc, there would be a few customers that think they can give it a go themselves. Not enough to effect a good round, but you always get have a go hero’s giving these things a go!