I’m travelling to the Languedoc in April. I’ve just booked my train ticket to Carcassonne which comes to £143.50 return. It’s a very civilized journey. I get a late afternoon Eurostar from St Pancras to Paris, then the sleeper from Paris arriving at Carcassonne at 5.30 the following morning. There are a couple of minor hassles: the transfer from Gare due Nord to Gare d’Austerlitz in Paris (metro fare € 1.70), and the very early morning arrival, but that is all.
Compare that with the Ryanair option at £119.66: It’s only £23.84 cheaper, but so much more hassle and additional expense. The flight is at 9.30 a.m. which means you have to be at Stansted for 7.30 to check in. Unless you live nearby that rules out using public transport to get there, and you’ll have to get up in the early hours. You arrive at Carcassonne at 12.50, but after you’ve got through baggage control you still have a 25 minute bus ride into town costing €5.0. Realistically, you are not going to be in Carcassonne until 2 p.m at the earliest, so you’ve saved half a day over the train journey, but you are probably going to be too knackered to enjoy it.
In my case, as a non-driver travelling from Sussex, I’d have to get a taxi all the way to Stansted, making the air trip far more expensive than rail, but that must also be true for anyone paying parking charges at Stansted for a couple of weeks.
Even the difference in time spent travelling isn’t as great as it appears. From my front door to Carcassonne is around ten hours by air and sixteen by train, but the extra six hours will be spent asleep, and most of the rest of my train journey will be reading a book or admiring the scenery, avoiding the hell of an airport check-in.