Identify what has changed since the enquiry
Tell the team whether the change concerns access, room availability, evidence or the person authorising work. Give the earlier arrangement as context and explain the current position. A brief message that the plan has changed may not identify which part needs reconsideration. Be specific about the practical difference rather than assume that the team can infer it.
For Hammersmith pest help, include any new observation without replacing the original report. Different evidence can affect the assessment question even if the address remains unchanged. The contact route provides a way to clarify the arrangement before attendance. Availability and any revised appointment need direct confirmation, not an assumption based on the previous booking.

