The Eurostar service to Paris or Brussels is a time saver if you already in central london. My employer is moving building to within 5 mins walk in Sept, so I anticipate a few friday night runs over to the continent soon! The run through the actual tunnel is very fast, no more than 20 minutes, and a rather non-event if you are an experienced commuter on the London Underground. The train itself is very much similar to the French TGV experience. All in a good way to spend the journey is standing in the bar with friends, arrival in Paris after three hours of 'after work' drinks is a classic experience.