Grey Dagger Moth Caterpillar

Thanks KarenL, no need for exact tree species since these species are not strict with their diet. They eat a lot of different species.

These ones are feeding on the Elm tree leaves but the other one is a different tree which I should find what tree it is and add it in the description.

Oh no, it's the same species just like this one but there are two, one a bit bigger. You can an old stage of this species' caterpillar on the spotting link provided in the notes.