Jane Austen wrote her major works in a period of twenty years, from around 1795, until her last published work in 1815. This means that Austen's adult life witnessed the French Revolution from its very beginnings in 1789 until the end of the revolution in 1799, when Napoleon ascends and changes the regime of France for good.
Napoleon's imperialist regime prompted an immediate war against just about everybody, and England responded by engaging the skills of one of its most beloved sons and soldiers, the Duke of Wellington. Wellington maintained a consistent advantage against the French, and against Napoleon, allowing England to only be just conservatively concerned with the war. This means that England was well-protected during this time period and the ways of life of the people were affected very little.
This is evident in Pride and Prejudice largely because Austen, even though has lived her entire life hearing about the French and their issues, writes very little to nearly nothing about it. In fact, the only effect of the war in the novel is the advent of the troops in the society of the marriageable ladies, and the effect of the soldiers in the psyche of society. There is no other palpable effect in the novel, other than Wickham, who is one of those very soldiers.
Another effect that could be drawn in society is that, with war and victory, you get a stronger economy. At this very time in history, England began also to experience the Industrial Revolution. This made England financially untouchable, and created a very solid, up-and-coming middle class who no longer depended on the feudal way of life to earn a living. This is why we see in the novel how so many people come to property even though they are not aristocrats, nor heirs.
If anything, the Napoleonic Wars made England quite a powerful and secure nation. Nothing was lost as a result of the War. If anything, the chaos remained in Napoleon's own turf (not to mention his own head). England was basically unscathed.