Open sky does not mean unrestricted reach.
Walls, balconies, planting, steps and glazed roofs can restrict a working position. Explain anything that blocks a direct route to the channel. Mention overhead cables and equipment already occupying the ground. Do not move heavy structures or climb onto a roof to create room for the cleaner.
Vacuum clearance is available, but it must be suitable for the gutter, debris and position. It is not evidence of high-rise or rope-access capability. The HSE introduction to working at height explains the need to assess the task and equipment before work starts.