British Library Database of Bookbindings is the source. Ivor Robinson and Edgar Mansfield are the search terms. Here are the results. Enjoy! (UPDATE, 11/18/2016: For a few more Mansfield bindings -- not held at the BL, but whatever :) -- see the following blog posts from Herringbone Bindery, and here, here, and here.)
What I notice are the flat spines. Elongated typography (on the 2nd, at least). Obviously there's lots of heavy abstraction. And some bold colors, but in sort of a restrained way, always over a deep, consistent background. Not necessarily lots of gold -- excepting the first one of course!