With repeat cleaning and providing the conservatory is in good nick then I'll clean everything from the gutters down in the price.
How much depends on how big the conservatory is.
Con roofs are way more expensive than just the conservatory of course, but again, that depends on the size and the state it is in.
I don't charge a specific hourly rate though as my target rate when actually doing the work is a £1.00 a minute....tell a customer you are charging £60.00 an hour and they'll have a heart attack!!
And no, just in case you wonder...I don't earn £60 an hour over a working week!! That is very specifically £1.00 per minute worked (as against talking to customers, driving between jobs, setting up and so on.
Ian