I was poking at timetables for another trip and I stumbled across a little tidbit: Apparently, Eurostar is running a once-a-week overnight service from London (Euston) to the French Alps this winter. I can't say as the idea thrills me (9-10 hours in a daytime seat as far as I can tell), but it's interesting to see this pop up on the timecard all the same.
https://content-static.eurostar.com/documents/UK_timetable.pdf
https://content-static.eurostar.com/documents/UK_timetable.pdf