If it wasn't for us being an AONB etc I'd have built a green roofed, passive esque "tiny house" for my lad (and I've have finished it). Got the land, no overlooking neighbours etc. Then there's council tax implications too. Barstewards! An Englishman's home etc. I think even a garden room is a no no where I am without pp. When you consider what the illegal beds in sheds brigade get up to.