Personally i wouldn't used a jet washer to clean a conservatory, its invalidates the warranty and your insurance will not cover it!
You might want to think about getting conservatory installation insurance, which would cover you for fixing, maintenance and cleaning of conservatories, especially being on top of them, which general window cleaning will not cover
I use a gutter vac for clearance of gutters and a hose for internal cleaning should it be required, generally its not as it cannot be seen.
Conservatory cleaning is mainly summer work, however if you make a real go of it, you may get all year round work from it.
Due to increased working hours from extra light in summer i also take one offs on providing it doesn;t interfere with my regular window work.
Usually leave them for rainy days, when window cleaning isn;t always suited.