The Eurostar leaves Gare de Nord about 8 times per day for London and you can reserve your ticket online. It is a little confusing, but with a little patience one can figure it out. Get your reservations at Eurostar. Be patient, try lots of combinations of dates and you can get a reasonably priced ticket. You choose the outgoing ticket and time first, then the incoming, but the prices are totaled at the end. Choose the flexible date choice, so you can see several possibilities at once. The best dates to travel are apparently on Saturdays, and over a w/e. This really is a busy commuter train, so weekday trips seem to sell out earlier. I traveled Sat. morning and back on Monday early evening for 101€.
You should get to the train station about 30-45 minutes early, and follow the Eurostar signs to the BILLETS(ticket)booth, where you will get your aller/retour (roundtrip) train tickets and your seat assignment. If you get the ticket in France, the ticket is in french (:)). You then go through security, which is upstairs in the Gare de Nord, and that was pretty self-explanatory, once we understood that that was what we had to do. Now, after security, passport & ticket in one hand, luggage in the other, you have to look at the monitors to figure out your train gate, but they were clearly illuminated, and everyone there was really helpful.
Then, you take a conveyor belt down to your train. Now, look on your ticket to see what car (voiture) you are in...but you have to look on the ground for the train car numbers. Your seat assignment(place assise)is the last number listed. The 2nd class seats are comfy, and for the less than 2 hour ride, were perfectly adequate. The restrooms are between most of the train cars. There are two food cars, but a lot of people brought food with them. The bane of everyone's existence was the guy on the cell phone, or the two women yacking it up the whole time. Headphones would be nice, but were not offered. I will take some with me next time.
The train from Gare de Nord goes right to the Waterloo Station in London. They may be moving that to another train station but for now, it is at Waterloo. From the Waterloo Eurostar you can get to the Waterloo Tube station. I bought an Oyster Card, which allows you to put money on an electronic card. I put 34 pounds on the card. That's enough to buy the card (3 pounds) and 4 day passes (about 7.50 pounds each). It worked great and was very convenient. I would recommend it if you are going to do the tourist thing, and you don't do taxis. The pass works on the Tube and the beautiful red double decker buses. You can get anywhere touristy on the Tube or the buses, and our hotel was within 40 steps of our Earl's Court Tube stop.
The return trip was just as easy, and there was an expensive, but convenient service called "Left Baggage" where we could drop off our bags on our exit morning and then come back and pick them up before getting on the train. The cost is 6 pounds per bag, but it was a lot easier than taking the bags with us for the last day of sightseeing.
Taking the train was really easy, and convenient. Now I am looking for sleeper car tickets for a trip to Venice.
