Thanks to R today who found this fab video on making marbled paper via @simongoode on twitter. If you can get past the amazing 1970s infomercial do-be-do music at the beginning it's actually a far more detailed look at the rather closed world of commercial marbling than is normally allowed and, in this case, we're peeking into the world of some of the best because this film was made at the Cockerell paper workshop
Simon Goode, who pointed the way, also pointed my way to the London Centre for Book Arts, whose website is well worth a visit.