Call the non emergency number 101 and explain what your going to be doing (vermin control)
They will take your details. Name and address. Location of where you are going to be undertaking the vermin control. Times etc. vehicle your in.
You are then issued with a number.
When your done. Ring them back and let them know.
But plan for this. It took me 25 mins to get through the other night on a job. And another 15 to tell them I had done.