Found on Beach in UK. Anyone able to provide ID?

Crustacean-like shell - segmented and flexible like a lobster tail, but rounded. Missing head. Underneath had some structure that dangled like legs, so likely the abdomen portion? Orange eggs included as a bonus.

Looked up various things with no luck (lobsters, crabs, shrimp, other arthropods, isopods).

AI outputs sea urchin.