I really enjoyed this. I've not been to Scotland and so don't know the geography, but could picture the newly evolving "features", like the ragiing river at the bottom of the garden.
As a side note, we'd visited Barry on the weekend where a nearby cliff had recently collapsed leaving caravans dangling over the edge www.bbc.co.uk/news/uk-wales-south-east-wales-15540048 and we could see it from there. And it was tipping down with rain and blustery
So it was things like that that I was envisioning. Actually, I was so caught up in the story I was reading it in the car on the way there.
Again with the geography, it seemed like Gavin was covering a lot of land. It took him and Jen a long time to get to the hut and hardly any to get back to Edinburgh.
As a future, this story sounded quite plausible. Rules and regulations at each turn, it was quite scary. It seems it was easy for one rule to follow another until it got out of control.