Just caught up with the water tower episode - wow!
It wasn't a question of things going wrong, amazingly, but more about the lack of funds and labour which have hobbled the project. And it was still just a project - 5 years in the making and hardly anything to show for it.
But the finished house in Devon was absolutely amazing, though the owners had virtually 3 x the budget and probably an army of specialists building it; the project in Northampton was basically a one-man show with little previous experience.
I thought Kevin was rather unfair and harsh on them in his summary, so I'm glad he took them to the Devon house to show them a glimpse of what their finished house could look like. I hope he (if he's still alive and able) revisits them in 10 years' time and see if they've finished it, they deserve it if only for their ambition.