Though a Londoner, I have visited Greater Glasgow many, many times over the years and I deliberately avoided the Braehead shows for that very reason. I knew its location and I doubted there would be adequate transport arrangements after the show. Sadly, my doubts were realised.
Good luck with Chalke Valley.
From my past experience, the events are all seated but there is no raking. That could be different now but that's how it was. Many of the events offer the opportunity for a "Q & A" session (questions and answers) after the presenter has finished. I don't know if that will happen with MK but it happened at Bridport and there is no reason for it not to happen at Chalke Valley.
You do see the various presenters wandering around the site (and some go to see other presentations). The other presenters will commonly be journalists, writers, politicians and the like but often with high profiles from television appearances. The Chalke Valley festival tends to be a polite and rather genteel event, in my experience.