[Fleecewife]

I think this:  http://www.carpentry-tips-and-tricks.com/stable-door.html#  is what Mr F found particularly useful. 

Doors are under construction now.  The frame itself is way more complicated than I expected, but then the builders have left us with two different sized doors, and some problems to sort before the frames can go in.

[bazzais]

You'll find that eventually it all goes to s**t and you just have to cope with the crap, animals and damp.  With a door that suits you.