Can you go to a large library and have a look/see first? I've got various titles on the shelves here (book-aholic.. and my college library sold the old books for 20p!) and the Dewey codes for such topics seem to be from 650 through to 658. Though I agree that there's unlikely to be just one book, one covering the NVQ syllabus should have the basics in.
If you are buying, remember to see if there's a choice of second hand options on Amazon and check out Ebay too.