In the 1980s, when author Jilly Cooper and her family moved a couple hours outside of London to the upscale rural enclave known as the Cotswolds, she soon learned the local pastime was sex. And lots of it: “Everywhere I looked people seemed to be committing both adultery and fornication.” Those neighbors would become the inspiration for her novel “Rivals” and its juicy story of desperate housewives, philandering husbands and the ruthless world of independent television in 1986. The book is happily sordid, with the soul of a trashy nighttime soap, and it has been adapted for TV with that same frothy spirit for Hulu starring David Tennant as the wealthy, cigar-chomping media executive whose TV empire ties it all together. There are rivalries as far as the eye can see in the fictional Rutshire County, populated with egomaniacal scoundrels and the women who seek pointless validation from them.