I had the pleasure of a bump up to a Conservatory room at the Four Seasons London (off Picadilly) during a recent 1-night stay. They are on the 2nd floor (yes, 3rd floor to us Americans). They are wonderful when the sun shines and very nice the rest of the time. Rack rate on these rooms is 500 pounds at this writing. The Intercontinental across the street is under construction, so the rooms facing away from Hyde Park are the only quiet ones.