I'd like a 'Lessons Learnt' episode of Grand Designs

It must be Grand Designs season on this blog, coz this post makes two in a row about the show.

That show's been going for over ten years and they've probably featured around 100 homes.  So what are the lessons learnt?  Are there any lessons to be learnt?  Any common patterns to successes or to failures?  Any other types of patterns (concerning: aesthetics, construction materials, amount or type of planning done, use of experts, etc etc)?

It could make for an interesting episode.