External pipes below ground level

[Timmy D]

TimmyD has more experience than me as a pest controller but the way to usually get rid of an infestation of mice/rats is load the area with decent poison, wait for say 3 days or so and inspect your bait boxes and repeat until the bait no longer disappears. I'd permanently fix a metal vent/grate across that hole as they'll gnaw through a plastic one. That looks like nesting material that's been dropped at the hole/door and that trap should be placed along the wall, they usually follow the outline of buildings for safety.

Spot on. Use 5mm mesh.