There’s an essay on “Romantic Quest in the West Midlands. Staffordshire and Cheshire Landscapes in ‘Sir Gawain and the Green Knight,'”, in the book collection of essays The Gawain Country: Essays on the Topography of Middle English Poetry, Leeds Texts and Monographs series, 1984.
The essay is not online, but the book may possibly still available by mail-order for £9 — according to this order page which dates from about circa 2011. (Update: no, still totally out-of-print and not online, at early 2019). It also appeared as “Staffordshire and Cheshire Landscapes in Sir Gawain and the Green Knight” in the North Staffordshire Journal of Field Studies 17, 1977, pages 20-49.
Incidentally, the pentangle on the shield (seen above) is not a pagan artist’s modern imposition on an ancient text, it’s something detailed in the text…
It is a symbol that Solomon designed long ago
As an emblem of fidelity, and justly so;
Therefore it suits this knight and his shining arms,
For always faithful in five ways, and five times in each case,
Gawain was reputed as virtuous,
The Folio Society found a way to detach the symbol from its contemporary “naff hippie-shop pentangle” connotations, by ingeniously and elegantly making it more like a figure…