40 ft sounds about the length you need, they usualy come in 6 or 8 ft sections so a 6 ft closed would probably be about 8 ft with all sections and a brush head, this type of pole will be quite heavy so for doing ground and second floor windows I have an ionics residential 12 ft pole comes in 3 sections of 4 ft so when closed you only have 4 ft pole which is handy for doing ground floor this pole is very light and I think it is about £90
cheers,
Temps.