Q.I Have The Tops Of My Small Seedlings In The Greenhouse Being Chopped Off And This Morning Sweetcorn Seedlings Had Their Seed Destroyed
but did find a slug nearby. However, on the other side of my greenhouse, I found a couple of pots with a pile of shells in them? The shells are very thin as you will see in the uploaded photo along with the seedling destroyed there also, any ideas please?

Certified GKH Gardening Expert
Here are some possibilities:
https://www.gardeningknowhow.com/plant-problems/pests/animals/what-animal-is-eating-my-seedlings.htm
https://www.gardeningknowhow.com/special/greenhouses/greenhouse-plant-pests.htm