Second hand Bookshop near the Catherdral in Liverpool has a brilliant local section. Got a few on Wirral and Birkenhead there myself.
Reid of Liverpool, Mount Pleasant. The local books face his sales desk.
Other good shops include Cheshire Books at Lady Hayes and another second hand bookshop on London Road Liverpool - Henry Bohn Books (round the corner from the Empire theatre). Lots of Wales and railways books there, and loads of cheap OS maps upstairs.