I've finished your most recent British Vogue infobox. Here's an article you might want to read about the rise of celebrities as cover models for fashion magazines. Another resource you may find helpful for figuring out cover models is thefashionspot.com, a forum of obsessive fashionistas that document basically everything that happens in any fashion magazine of any importance. (Along with full-color scans of pretty much everything... it's amazing they haven't been shut down yet!)