I'm an American who discovered this show just this year when a couple of seasons of it were on Netflix for a while. I fell in love with how different it is than American home improvement/building shows. (Also I think about Irish castle guy all the time and wonder what's happened in the years since.) When I saw this nominated I was like, "Uh...what would a fic for it even be like?"

But you absolutely sold me with this: I'm eager to see Grand Designs crossed over into some kind of genre setting, original or otherwise—supervillain lair, superhero HQ, haunted house, portal fantasy, etc etc. I super hope someone writes this for you!