I still disagree, with both the OP and my fellow countryman (Emmanuel_M), and would beg to disagree with their analysis.
Having play numerous games with France, I never had troubles to invade UK, assuming the following :
1) I do distract their fleets, before they regroup, usually it mean hit them hard with my best (Latouche Treville) near little Brittany. They will come piece meals, so it is not that hard, I am close to my ports, so I can easily back up and take care of the wounded ships.
2) I let them , invite them even, to invade northern germany,
3) I proceed BEFORE jully 1804, past that date (plus or minus), they will produce more ships than it is possible to sink.
4) the invasion goal being to capture a sea port close enought to reduce risk of interception.
Let say out of 30 games, I was able to do it 29 times (the missing one being the first i played, before I came with that strategy).
But Time if of the essence, you can do it only during the first 6 month, after that is too late.
So how to do it ?
1) Day one, ask Spain to honor the alliance, Nelson will wste time in the Mediterannean sea
2) regroup your fleet in Rochefort, hit and run untill they are regrouped
3) move your army in Germany against BRunswick, and let it there (do not make peace with them). UK will send an invasion force.
Results during a lasps of time , UK fleet will be spread into 3 theaters, while you will be grouped in the channel; so arrange for naval battle , and during it cross with the transport, take a sea port, back up your remaining ships.
While your invading force start to take provinces, your flleet will reinforce, and you will able to transport some more troops (if needed and if disponible).
Good timing, set up a strategic trap, and audacity are paramount and will lead your forces to victory. If not, as in history, you will simply loose on the long run. Going bull head against the RN is also wrong, the French navy did not have the capacity at that time, and that is reflected accuratly in the game, maybe too much for many of us, but it is the sad historical truth, any encounters (but the 3 lost by Nelson) were defeats, because moral superiority, technical superiority, training superiority, command superiority. Those 3 defeats from Nelson were due to the cunning of the french commander, so you have to be cunning too.
P.S. I do propose a strategy, but others here did propose other strategy; mine work for me, but others are fine too. The only real point being : you must find a strategy that will allow you to by pass the RN superiority.