hi gavin,
interesting project... ay least because I'm doing something pretty similar!!
I agree about concentrating just on the building and the closest area, otherwise you'll need much more than an A4 sheet..
about the size of the door and consequently of the other fittings, I just returned from a tour in normandy (well, it was disguised as a romantic week, but actually I moved in the little towns with a camera and a measuring tape...) and, well.
it's true that the average french and european people is (was) shorter in the recent past, and that a door 200 x 90 is the actual standard, but you must consider few things: an entrance door, especially of a resident house, will be always bigger, for reasons of image and practical use: that was the door to introduce in your guests, and... your long tail piano!
so it's no infrequent to observe an house with a big main door and a little one in the back. same for the windows: the first floor big, the ones in the roof littlest.
finally, it's up to you to choose which type of building build, and which side of it show up... I prefer to start with an idea, and from that one let the walls grow around.
here some pics from my mark IV. I want a shed with reasonable low ceiling, a stair, and an upper floor with high ceiling and big windows... all in a little space. so first of all I started with some drawings withe the idea, as the your, then I cut in a cardboard the shed's door and go on with a human figure as comparison..
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obviously changing step by step. at now I don't have yet the definitive size, but I'm closing on them...
go on and show us your progress!!