This is an interesting suggestion and something I had wondered why no-one had proposed before, but I wonder if on cost it could compete with the low cost airlines which most people use. You often see mini-buses and even coaches of Polish at Dover and the Tunnel going back and forth and I wonder why we dont do something similar. It also occurs to me that there are quite a few Brits where one party lives in France and the other still works in UK and commutes, much like I do.
It is however something I may be interested in if there were a stop off at Limoges. My husband is out in France pretty much full-time and I try to go out at least once a month for a long weekend and then all my work annual leave. Until recently I was flying in and out of Limoges but I have had to stop this as I am terrified of flying and it was making me ill. I was not getting the best out of my long weekend as I would spend all the time worried about flying back!
Now I am using eurostar and the TGV, the journey is double the time but I can work on the laptop during the journey. The cost is also somewhere between 2 and three times more than flying. A bit like the flights, if you get the booking early enough you can get some bargains. I tried researching coaches but could not find anything.