Oast houses are a feature of Eastern and Southeastern England, particularly Kent. So you can imagine on at Hunsford if you wish, although they also crop up in Surrey (around the town of D__________ , and certainly near to Box Hill) and also in Hampshire. Jane Austen would have been very familiar with them, being as how Chawton is near to Alton, and Alton was a major market for hops. Beer again, you see. Most oast houses are round, and originally would have no windows. The two storeys would be used as follows:
The ground floor was a fireplace. The upper level was just open beams, radiating out like the spokes of a wheel, onto which were placed mesh screens. the freshly, harvested hop heads would be dried on the meshes before being taken to the brewery.
The single oast house has no windows- does that mean it's still in use? It has the turret-like roof, but no chimney vent, so maybe it isn't. The triple row of oast houses do have their cute chimneys still, but also windows... which means that they are almost certainly converted into dwellings or other uses. I must admit, it would be fun to live in one. And, just for the record, I think they are a product of the Ag Rev and later- certainly the concept isn't nearly as old as malt houses.
Both these photos are from Geograph, and they are both Kent.