Deidre Le Faye's "Jane Austen, The World of Her Novels," also makes the point that a "cottage" back then meant something other than what we think of. As evidence, she gives this advertisement for the auction of a cottage, from a 1809 Hampshire Chronicle:

A Neat, Elegant, and Very Convenient Freehold Cottage Residence ... containing a drawing-room, eating parlour, breakfast ditto, six bed-chambers, good kitchen, convenient offices, with excellent wine and beer cellars; and, in a detached building, menservents' rooms, coal and wood houses, coach house, stabling for five horses, granary, dog kennel, &c. The Cottage has southern aspect with a verandah to the sitting rooms on the ground floor, which opens to a Paddock or Pleasure Ground, skirted by the River Itchen, well stocked with Trout; the kitchen garden is fully cropped and planted ... the Gardener will shew the House and Grounds ...

Le Faye comments that "Barton cottage appears to be not a great deal smaller than this one." (pp.132-33)

I'd forgotten that Chawton is a cottage, and it does seem Barton-like -- though it's set in a village and seems less isolated than Barton does. Note also that the cottage being auctioned above is a "freehold," not an adjunct to a larger estate -- though perhaps it originally was one.