Just looking through my old collection of partial Silurian (Wenlock Series) UK trilobites. With this piece in particular, as I'm trying to find a close match to the possible bivalve nestled next to the partial cephalon.
So far my best guess would be Goniophora cymbaeformis if the fossil is a bivalve. Looking at a description from my British Fossils Palaeozoic hand book.
Any and all suggestions are most welcome, I can't prep the shell any further than what you can see I'm afraid.