Phil...get some strong tape and tape a cloth/dustsheet under each pane near the walls, as you go. The drips are normally like treacle and drip on the walls and stain them. I used a customer's karcher vac on one and am considering buying one as it helped with the drips. All the frames will need cleaning, even if the customer says just glass, you'll have to do the frames too. Watch out for sun in your eyes and wasps.
Pricing?: Assuming it is a first clean, allow minimum 3 hours for a normal size conservatory you'd find on a typical 3 bed semi.