A friend and neighbor of mine (here in the San Francisco Bay Area of California) has recently created a web site about GB booklets. It only covers pre-decimal booklets, but since that includes the early Machin booklets, I mention it here.
Of special interest to us is his page on the first prestige booklet, Stamps for Cooks (affectionately known as the "cookbook.") He outlines the history of the booklet and shows an early mockup produced by Stuart Rose (the first Design Director of the British Post Office), a pane from a proof booklet constructed from counter sheets, a pane of dummy stamps, and a promotional poster.
The site's home page is at https://sites.google.com/site/gbstampbooklets/home (link). The introduction is here. The Machin page is here. The Stamps for Cooks page is here.