Short answers, pulled from the story.
Horsehay roughly means "an enclosure for horses," with "hay" indicating an enclosure in place names. The name dates back no earlier than 1759, and as late as 1981 locals pronounced it "Ossay" in dialect.
Abraham Darby II founded Horsehay Works, with the furnace coming into blast successfully on the 5th of May 1755. He enlisted financial backing from Thomas Goldney III, the main shareholder of the Coalbrookdale Company.
Horsehay Works contributed to the birth of the Industrial Revolution through large-scale iron production, making the East Shropshire Coalfield the greatest iron-producing area then known. The works produced large-scale products including a railway bridge in nearby Shifnal and later prefabricated bridges for export around the world.
Edith Pargeter was born in Horsehay in 1913. She wrote the popular Brother Cadfael novels under the pen name "Ellis Peters."
William Ball was an ironworker at Horsehay Iron Works in the early 19th century who was, at the time, the heaviest man in England at 36 stones. After an eye injury ended his ironwork, he toured the country as a celebrity under the name "John Bull."
Yes, Horsehay is still home to the Telford Steam Railway. The railway arrived in the village in 1857 and by 2017 was holding events including a 1940s weekend and a Polar Express experience at Christmas.