What ho one and all,

While cleaning today, I found in the dark recess of a cupboard that is effectively, our plant room (HW cylinder and boiler cupboard) a pile of soft stuff; no idea what it is but vacuumed it. Thought it may have been coming from some insulation around the top of the wall hanging boiler.

Checked again just now, and at the back of the cupboard on the floor, I see ants. They appear to be coming from a very small hole where the Fermacell and screed meet.

I don't like eradicating insects but I also don't want ants nesting in the timber frame / Warmcell. Google tells me how to prevent them coming into the house but what is the best way to eradicate them from where I cannot see?

Thanks