Wow, who knew a librarian's job could pay that much...
It's surely for those positions that require a master's degree in Library and Information Science ... in which case 30,000 pounds is a good salary, but not amazingly good. Someone with the actual title "librarian" is an information specialist in charge of organizing information and databases, and usually isn't the one who checks out the books for patrons or reshelves titles (unless, perhaps, it's a small library or they are understaffed at the moment). The person who has the title of librarian, as opposed to being someone who works in a library, is like an upper-level position, ya know?
I know that doesn't have much to do with salaries in general, but I thought I'd just mention it (don't move to the East Midlands hoping to earn 30,000 for stamping return dates in books!)