Some 70 years on from his rock ‘n’ roll heyday, Buddy Holly is still as ubiquitous a figure as they come in the rock realm, worshipped by everybody from Elvis Costello to Keith Richards. One of the biggest appreciators of that thick-rimmed, bespectacled revolution, however, has always been Sir Paul McCartney. The Beatles were endlessly indebted to the first wave of American rock and rollers that drifted across the Atlantic Ocean, but Holly was …