Thanks Baz,
As far as Sketchup are concerned it is a known bug - I just got this email from Yogesh in the Sketchup team:
*Hi Sam,
Thanks for your note.
We have two other post with the same issue
https://forums.sketchup.com/t/layout-scenes-and-scale-nightmare/34813
https://forums.sketchup.com/t/sketchup-2017-scenes-not-working-as-expected-in-layout/34210
And as mentioned by Marc in https://forums.sketchup.com/t/sketchup-2017-scenes-not-working-as-expected-in-layout/34210/11 we are working on a fix. Please check the release notes for the future maintenance releases of 2017 for official word that it's been fixed and also subscribe to the about forum posts for any further updates .
Please reply to this email if you need further assistance with this specific issue.
Regards,
Yogesh
The SketchUp Team at Trimble Inc.*
Marc's (from Sketchup) post said the following:
This is a bug related to the graphics refactor. It will affect scenes that don't save one or more of these settings: camera, shadow, axes. We've got a fix in progress!
I've been advised by DaveR and Sonder that scenes should be used for every viewport which I'm looking into and testing on some current projects - thanks again for your advice on the other thread DaveR and Sonder. Sonder - I bought your book too. Some great templates, resources and tips in there and some new working methods for me to test out - thank you.