In the end, I've been forced to throw away all the existing work because the quality was so poor, and start again. This will actually be a boon, because it means I'm rewriting with modern functionality such as flex, which will simplify things a lot. I have the site building all its pages, but only with the banner and main menu for now; the complexity of the submenus is going to take some figuring out. I've ported a bit more content into the data files so that I have stuff to work with, and in the process made a number of updates to the schema and the Oxygen Author Mode CSS.