Hi Pete - loads of possibilities re your questions
I would get a decent double pointer 3-4m - they are safer than normal ladders if used properly
don't use the light stuff - your life may depend on it
get a single pointer maybe 6-8 feet
conservatory roofs I can't comment on
the hard to get to window eg over garage/conservatory does not clean easy with the pole - you can get the dirt off but it's hard not to leave streaks because you aren't using the same dexterity as hand held squeegee
Why do you want to change careers, if you don't mind me asking