My dad would often reference this film, which he saw as "Tight Little Island" before it was officially released, as he was coming back from Hokkaido after being in the army of occupation there. (Trained as a paratrooper, he was the postmaster the three years he was there.) He laughed that it ruined his idea of a Scottish accent for years afterwards, and as he told many jokes and was in community theater, that could have been a problem. However, people knew even less about the various British accents then than they do now, and I don't think anyone ever noticed.
It is based on a true story of a small island banding together to keep the whisky that had fallen into their laps during wartime rationing. The book was apparently more serious and literary, and the author was displeased.