.308--that's a well built hunt cabin. I like the foundation--never thought of that, I'd used concrete blocks, but they've shifted over the years and now my camp floor is a little uneven.
What would something like that cost you (as is) in the USA?
As for propane heaters--I've been using the Big Buddy heaters without any problems, but I can tell ya they're brutal on propane consumption.
The only negative--on a dark night, the darn thing can keep you awake with the glow that comes from the element--it gets really bright in the cabin.
This year I want to install a small wood burning stove, but then I'll have to figure how I'll stoke it during a really cold night .
As for water, you can either run a gutter on the roof with a down pipe to a 60 USG blue plastic drum--or fit a 3/4" valve and fill the drum at home and take it up to the cabin. I'v done both at mine--you'll always need the water, especially after dressing a deer.