OK people . . so major progress today 
I eventually worked out the problem (stupid obscure security setting in github preventing the sync), and now have everything talking nicely together and setup.
A lovely person on Gitbook slack has given detailed instructions for the supposedly extremely simple process of installing the plugins and I’m going to have a go at that . . we’ll see what happens
I am not 100% clear on the user permission syncing, so have invited both @sstead and @simoneluijckx to gitbook (as owners so you can invite others) but need to then check back how this syncs with github, so we can hopeuflly use github to get around the five person limit.
Have created project management page to keep it all together and closing this thread to create new one for this next stage.
Project Management page