It's full of little people; they had to go live down there when a new leisure centre was built.
https://www.google.co.uk/maps/@52.5329433,-2.4172067,3a,75y,300.1h,90.91t/data=!3m6!1e1!3m4!1s2sCSkL61lI5CRujg33EJeA!2e0!7i16384!8i8192?coh=205409&entry=ttu
Some are posher than others https://www.independent.co.uk/news/uk/tiny-shropshire-cottage-boasts-impressive-cave-in-basement-a6821221.html and sheep live in 'em.