I've just come across
Windmill Walks, which offer,
to quote the site:
a series of walking guides featuring circular walks that use a windmill as an excuse, if ever one was needed, to
explore some of the magnificent countryside that rural England has to offer.
There is certainly a Kent edition, with 18 walks included, where each walk includes a detailed guide and map, plus
a photo and description of the mill. Sussex and Surrey guides appear to be in the process of preparation.
Windmill Walks