It's not a sleeper service as such but the Eurostar overnight ski train to Bourg St. Maurice is amazingly time efficient. Leave the office at normal time on a Friday, pick up the 8pm from St. Pancras and be on the slopes first thing Saturday. By air, the earliest you could hit the slopes would be after lunch on Saturday, and that's assuming you take a stupidly early flight which gives you no sleep (like the train), and that you hit Geneva and the motorways on a (rare) benign day. Same on the return.