Wasn't at Hensley Mill last weekend but I've been there twice before and that place genuinely unsettles me. First visit was a few years back, broad daylight, and I still felt like something was watching from the upper floor windows. The second time we went at dusk (yes I know, cliché) and one of our group swore she caught movement in her peripheral vision near the old wheel housing.
Shadow figures are interesting because they keep coming up across so many different locations and cultures, they're not just a British thing. Whether its residual energy, something intelligent, or just pareidolia I genuinely can't say.
Would love to hear more details from whoever saw it. How long did it last, did it move with purpose or just drift, was there any sound? Those details really help narrow down what you might be dealing with. Anyone else planning a return visit soon?