I would also consider Köln (Cologne) via the tunnel
Hello London citizen
I've been traveling a lot, and even if the train takes a bit longer, the nice thing is your sitting down reading a book (or preparing a PowerPoint presentation if on work) while doing it. London St.Pancras to Köln takes about 5h. Köln has nice Spas rather close to the station, and, there is a fabulous Spa called Mediterana just outside Köln in Bensberg.
Cheers
/Halkan
|