The French army was actively engaged in war from 1792-1815, fighting on multiple fronts. The British army had less experience, as it fought on and off, and generally, whenever Britain's politicians decided it should. The French soldier was for the most part fighting in the defense of France (1793-1806) (1813-1815), the British soldier was not (fighting in the defense of Britain). Overall, the French army had many, hardened, well trained soldiers. Britain's men may have been better trained, but experience is pretty much like another form of training. That's my two cents.
The British army was actively engaged in war over the same period (actually first involvement was in 1793 when a British led force landed at Toulon) fighting on just as many fronts:
Denmark, North America, Iberian peninsular, invasion of France and finally Waterloo.
Not only that but the British army was actively engaged in colonial wars such as in India where Wellington (then Sir Arthur Wellesley) learned his warcraft in major battles like Assaye.
If there was a contest in experience, the British win. Moreover France suffered some severe defeats - none larger than their almost complete destruction in Russia.
The reason why British troops consistently beat French troops over the period was their superior training. It is well documented that British troops trained and trained with LIVE ammunition so as to maintain their murderous 4 rounds a minute ROF.
The British infantry was peerless at that time - none more so than it's elite light infantry armed with rifles rather than muskets.
I don't see how the goals of an armed conflict affect a soldier's training and experience levels, but I would argue that Britain fought the Napoleonic Wars in order to defend Britain.
Yes, Britain engaged in expansionist conflicts but so did France (Napoleon's ill fated Egyptian campaign and the invasion of Russia).
It is not widely known but the majority of losses in Napoleon's 500,000 strong Grand Armee that invaded Russia, were suffered before they got to Moscow (mostly disease and desertion).
A major problem Napoleon had at Waterloo was raw, young, untrained troops because Napoleon was so profligate with the lives of his soldiers.
