I took the TGV back from LYS back in in March, complete with connection at Lille. Left Lyon at 17.00 and was back in St. Pancras before 21.00. Complete with being fed and watered by the lovely Eurostar people with a better meal than one would get in Club Europe meant it was a rather pleasant experience and no schlepp to/from the airport and no faff with security. Really quite pleasant.