Still confused about Oyster cards vs. travelcards

Your plan sounds very good. You might not even need 20 GBP in pay as you go. I am assuming that you are traveling solo; if so Oyster is the way to go. It is all less complicated than it seems. The Oyster Card is just a plastic smart card that stores your tickets and it can store a travelcard or pay-as-you-go money or both. A weekly zone 1-2 travelcard costs just 29.20 GBP and it is valid during both peak or offpeak times which makes it a better deal than doing everything with pay as you go. Buy your Oyster card when you arrive in London (go to the ticket window in the tube station, not the rail station). Tell them you want to get an Oyster card and load a one week travelcard starting that day plus 20 GBP (or whatever you decide) pay as you go. 20 GBP might be more than you need. You can always start with less pay as you go money and add more later. There are machines in the tube station where you can check the remaining balance and then "top up" the card with more and many will accept cash. You will pay a deposit on the card. If you want to get that deposit refunded, make your payments are all done in cash and try to make sure that you don't have a lot of money left on the card at the end of your trip.

Thank you very much. I am traveling solo but am meeting a friend in London for the first 2 days I'll be there. She's traveling by rail from Leicester and I told her about the 2-for-1 discounts for the London Eye and Tower of London, which we will visit together.

Sarah, if that is the case then putting a weekly travelcard on your Oyster will be as much good as a chocolate teapot. It will cost you money. If you want to save money by doing the 2 for 1 scheme underwritten by the railways then you both need a proper paper rail ticket valid on all the days you want to do the 2 for 1. Your friend presumably is going up to London from Leicester on the East Midlands railway into St Pancras station. If she uses a combination of Advance Singles availablke for cheap on the interweb then she won't have a valid train ticket during the stay so you can't use her ticket for her "proof". If she has a Saver or Open Return it will be valid. If you have no return ticket then you will need one for the scheme. If you get a Rail issued paper weekly Travelcard then that will do the job nicely. If you buy it from an Underground ticket office and it is put on your Oyster Card it will not work. You need a paper ticket with the British Rail (National Rail) crow feet (arrows) logo on it. Yes, you can easily buy a paper Travelcard at St Pancras when you arrive - do it at the East Midlands ticket office or the Southeastern Trains ticket office, both of which are around the corner from the arrivals area at Eurostar. You have to go back into the main station, away from the Euston Road end - away from the Underground end.

You could buy a one-day zone 1-2 National Rail paper travelcard for each of your first two days in London when your friend is with you. Then buy an Oyster card and load a seven-day zone 1-2 travelcard on it plus some pay-as-you-go pounds for your ride to Heathrow.

That's probably even better...

Tim's suggestion is very good. It makes a lot of sense, given that you will be travelling with someone else and want to use the 2 for 1 discounts. Another option is that you could just get a 7 day rail paper travelcard (you'd need a photo). You could get an Oyster with only pay as you go for your last couple of days. There are even more permutations, but I think you want to get a weekly card in the mix there somewhere; it will be cheaper than 9 pay as you go days.

Laura, Tim, and Nigel - thank you so much for your insights. I feel like I have a much better handle on this now. I'll follow Tim's advice to purchase two one-day travelcards so I can take advantage of the 2-for-1 discounts.