Just wondering on the off chance if anyone knows of a survey / artistic impression of the GG system that could be used on an information board up at the shake hole.
There's Scoff's (RIP) "map" in the style of the London Underground. I can't find an image on-line, I think I might have a photo with it in somewhere. I'll have a look, but someone in the BPC is sure to have a copy of the original.
There are issues to be addressed if using London Underground type diagrams, re copyright. Unless you want to spend time looking into the legal minutiae, it might be better to choose something else.
There may be something on here which would do (and probably be easier to get permission to use).