Caterpillars invading my hedgehog house

Caterpillars invading my hedgehog house

Observation - Caterpillars invading my hedgehog house - UK and Ireland. Description: I opened my hedgehog house roof to find these caterpillars nesting, each being about an inch long. I'd disturbed the top ones and they furiously started crawling around. I want to know what type of catterpillar they are and what they'll turn into.

I opened my hedgehog house roof to find these caterpillars nesting, each being about an inch long. I'd disturbed the top ones and they furiously started crawling around. I want to know what type of catterpillar they are and what they'll turn into.