How can I see the list of OBCZ in different cities/counties?
It's also possible that some of the listed OBCZs are no longer active, so if you see one it's worth checking the location, looking for recent releases, and even looking online to see if the business is still there; I've seen some sad posts about favorite pubs-with-OBCZs that closed down or changed management and dropped the book-swap shelves.
It's possible that some locations will have book-swap shelves, Little Free Libraries, or other similar things - not official OBCZs but still good places to hunt for and release books. But for those you may have to browse the listings for each city you plan to visit.
Other sites may offer some help: the LibraryThing site has a "little libraries" option where people can list Little Free Libraries, BookCrossing OBCZs, and any other book-swap location they come across. And there are other such sites, some country-specific, some international.
I've even had some luck doing a web search on a specific location and "Little Free Library" or "book-swap shelf"; sometimes things are announced that way but not on the official site maps.