Flew the year before last on easyjet (east midlands – geneva)
Got a cardboard bike box, prepped the bike as per I think the trailaddiction site (wasn't going with them) plus tiewrapped the bike bits + riding bag toegther, then agritaped (like duct tape, only gray .. ) all the edges/corners for durability, then wrapped the box in clign film (if it rains while your box is on the tarmac, the bottom of your box could drop out ..), then more tape on the edges
This year I took the train (actually one to london, another to the otherside of london and another to where I wanted to get to) down to a friends to meet up and car-share (via a ferry) to the alps
Aside from having to move a bike, 70L rucksak, camelbak + helmet between trains etc I think thats the best way
Some parts of france can get really dull to drive through though. Just gently rolling big fields with the odd generic settlement for 100's km