Hi
I would not recommend using a pressure washer on a conservatory, to much risk involved.
With reference to a pressure washer being attached to a wfp, yes, that is possible. You need the trigger at the bottom though; a good hacksaw and a length of hose will solve this!!!
Last week, I attached a hose pipe and spray nozzle to a 20ft extension pole. I had the handle strapped down so it was permanently on. This worked well for me, because I cleaned these gutters with my wfp and they where black, so not wanting to be around for ages waiting for the drips to stop so I could finish them, I reverted to that method. Attached the hose to an outside tap and rinsed them down in seconds.
Andrew