We will be staying in London for a few days before our RS tour starts in Paris and I thought it would be the most fun, and easiest, to take the train through the chunnel. I see I can purchase two one way tickets now for $156 for both(1 adult and 1 student). Is this a good deal? Should I also purchase the "london travel card" in advance? 3 day central zone passes are $41 each (is this the oyster card?)
Yes, buy the Eurostar tickets now. Unlike plane tickets, the sooner you buy Eurostar tkts the cheaper they will be. You can wait and get the Travelcard when you arrive in London, no need to purchase early. You can load up an
Oyster card at Heathrow or any tube stop or train station. You'll be able to get the same price in London. (I believe it's £17.40 for a 3-day Travelcard in zones 1-2.)
The seven-day travelcard can be loaded on an Oyster card, but not the one- and three-day cards. Those are paper cards. The three-day zone 1-2 card is sold only as a peak card (travel all day) and costs £17.40. The one-day card comes in two prices: £6.80 peak and £5.30 off-peak (after 09:30 on weekdays and anytime on weekends).
The simplest--and probably the cheapest--thing for you to do would be to load an Oyster card with about £21. Based on the rides you take, the Oyster computer will calculate the best fare for you. Each day it will top off at no more than 50 pence less than the cost of a one-day travel card, no matter how many rides you take. The deposit for the card is £5. After you take your last ride, you can get the deposit back plus any unspent money still on the card.
The clerks at any Tube station will tell you what will be cheapest for you.
Thank you both! I'll get the Eurostar tickets now and wait to get to London for the Oyster cards.