Saw the workers drilling holes in the building. One worker had a sweatshirt on that says Surefill Insulation so I looked them up. Their facebook page states:
Surefill Ltd is a family business, established in
2000. We install bonded bead cavity wall and loft insulation to new
build and existing private and commercial dwellings.
So I guess they were going to install some insulation. I never heard or seen this before but found it interesting.