I wouldn't worry about easyJet: they seem to be (in both my experience and from what I have heard) pretty reliable, and although sometimes late, they don't seem to be prone to be disastrously so – no more so than most full-fare airlines, in fact. But as noted above, be aware that any weight of hold luggage over their limit will attract an additional fee. They're very relaxed about the weight of carry-on luggage, however.

Regarding the trains: I've never encountered dirty WCs on a long-distance European train, so I don't think I'd factor that in to your travel plans.

The warning above about French strikes is worth noting, though. There's nothing you can do about that, but forewarned is pre-armed, and all that sort of thing.