as a Brit, one thing to take into consideration with driving is that if you are tired, the risks will be more for "going on instinct" for side of the road situations.
No clear answer here, but I do know that for some people, this could be a factor to make the train option work, just from not having to concentrate fully for a very long car drive.
Ive only driven a British car in France, which was weird, but at least I didnt have to think about which side of the road to be on.