we do at least 5 conservatory valets a week - bit more than just a roof clean.
price wise.
how dirty?
how big?
how long (time)?
good & bad access?
one off/regular (say 4 monthly)
thats what you should be looking at.
oh and if its plastic - then a simple cheap fb pole and customers outside will do the job
if clear then above and finish with pure wfp.
no need for a ladder against the conservatory most of the time! a pair of 5 -8 tred steps about 5 - 10 yards away from the conservatory and your wfp does the job.
if really dirty - then tfr,ubik or even silet bang sprayed on, leave for 5 mins, and then go over with the pole.