Oyster Card vs. 7 Day Travel card

Oyster card would be marginally cheaper for travel purposes, but you would need to get a refund at the end.

You also can't take advantage of 2 for 1 admission offers from a national railway station paper travel card.

You haven't indicated how you are arriving / departing from London or the exact area you are staying in to give complete advice.

Three one-day passes would be cheaper than a 7-day, especially if any of them are the off-peak version, for travel after 9:30 a.m. Mon-Fri or all day Sat or Sun, and in just zones 1 & 2. You get the sightseeing discounts if you purchase the paper Travel Card from a train ticket office, not Tube office.

Marco, we'll be arriving in London at Euston station, taking the ferry/train in from Dublin. Then we need to get to Paddington station where we will be staying for 2 1/2 days. When we're done site seeing in London, we'll be taking the Eurostar from St. Pancras to Paris.

So correct me if I'm wrong... We plan on buying three one-day paper passes at a National Rail Station like Paddington or St. Pancras. This paper ticket can be used to travel throughout Zone 1 via the Tube or hop on/off buses? In addition to giving us unlimited travel on the Tube/buses, we can also take advantage of the 2 for 1 offers when visiting London attractions?

And if we decide that we don't need the 2 for 1 discount, what's the best way to go? Three one day paper passes or the Oyster Card? Is it a hassle to get our refund back at the end of our stay in London?

Oyster. Buy your Oyster when you arrive in Euston. The machine will calculate each trip you make on it (tube/bus) and will automatically cap when you hit the travelcard maximum for the day. You won't pay more than you would have done if you'd bought the paper travelcard in the first place, and may pay less if you don't use it that much. Its easy to get a refund at the end of your trip; just allow extra time to do that and don't preload it with too much money. You mention the hop on hop offs - If you mean the sightseeing tours, the Oyster doesn't work on those as they're private companies, but it certainly does work on the regular big red London buses. In fact, after July 6, the only option for bus tickets will be Oyster or paper travelcards as cash is being eliminated.

As you're coming in to London on a train, you'll already have a paper train ticket that you can show for the 2 for 1s. Make sure you don't put it throught the machine when you arrive in Euston, but rather show it to the guard at the gate.

Your one way train tickets to London are only valid for the 2 for 1 offers on the day you arrive in London ie day of travel.