This movie version of the popular BBC show has elements that both work well and fall short. Expanding the story to feature film length gives more opportunity to explore the characters of Perry and Croft, yet simultaneously diminishes the rapid-fire comedic energy that made the original so effective. Regardless, it remains a very entertaining experience, successfully blending excellent sitcom writing from these two talented writers with a cast and setting that provides strong echoes of those individuals who were determined to contribute to their country's defense against the Nazi threat. The film uses the same actors as the television series and portrays how their unit was formed under the leadership of the somewhat foolish "Capt. Mainwaring" (Arthur Lowe). A more overtly comical military feel permeates the film – they practice drills, eventually using firearms (a questionable decision given their gas-powered van!), before participating in exercises overseen by the slightly arrogant "Gen. Fullard" (Bernard Arched). Predictably, almost everything that could go wrong does, but the humor is genuinely amusing; the writing subtly improves upon what’s visible and often expected, which greatly increases the enjoyment of watching it. It satirizes the self-importance of the upper class, the ambitions of a rising middle class, and the resourcefulness of those who seek to profit from any situation – perfectly represented by "Hodges," a part-time warden/grocer, and “Pte. Walker” (James Beck), a black marketeer. The film does revisit some ideas already presented, but it’s still a lively portrayal of genuinely brave people doing their duty.

Source on TMDB