Hi, lengthy explanation sorry
I believe it's a recurring theme here in Cornwall, one of the most common things I probably noted on Cornish housing as apposed to the more English way of building houses. Most of the cottages or even houses I've seen down here are built like this.
The chimneys are to the outside walls and the doors towards the centre, I believe because of the width of most of the 'cornish houses' were quite narrow and as you walk in the front door there's the stair case going up. In some cottages you need to duck slightly because of the height.
For example in my grandparents cottage they actually knocked in an additional window just above the stair case to let light in the toilet of the bathroom which they fitted it is tucked above the roof of the stairs on top of a step. My grandparents shown me some pictures of the cottage before they knocked the additional window in. Most common but before the toilet would have been at the bottom of the garden of which there are remains of it.
A good example of the style is the most famous railway cottages at Burngullow which are built with the living rooms and kitchens towards the centre with chimneys. The end two houses have the doors towards the outside and because of the width of the building the stairs are directly behind the front door and takes up most of the width of the building. None of the railway cottages have windows above the front or back doors for this reason I presume. I think you'll find Cornish housing is considerably smaller than some other housing mainly being built for china clay workers and minors, farms or even railway employees.
I assume most english housing have are either wider and have a upstairs bedroom or the stairs has a window above it to let light in on the landing.
Burngullow, September 1959 NRM
Just one of those little details, the cornish also have their own way of building hedge rows. Of which the hedge rows are built in a certain way to stop them falling over.
Cheers, Reece