The immediate concern may be a sighting, but the practical concern is often how to keep the premises functioning while it is investigated. A Gunnersbury occupier might need access to a home office, a shared kitchen or a room used by customers. Explain those needs alongside the evidence. That helps distinguish the area requiring assessment from the wider building and makes it possible to discuss which routines could be affected by the proposed work.
Do not assume that a booking automatically requires the entire property to be vacated, or that every activity can continue unchanged. The appropriate instructions depend on the findings, method and people using the space. Before work is agreed, ask about access to the affected area, preparation, cleaning and the return of belongings. If the property has restricted opening hours or an alarm procedure, arrange a contact who can provide entry and answer practical questions during the visit.
Written follow-up is particularly useful when the person arranging treatment is not the person using the room afterwards. The handover should identify what was done, which instructions apply and how new signs should be reported. Where repairs or further access are recommended, give those tasks to someone able to arrange them. Clear responsibilities reduce the chance of monitoring being moved during cleaning or a relevant opening being covered before its role has been assessed.