Discounts for London Attractions

For holders of a British Rail ticket valid on the day you visit the sight, there are a plethora of two for one offers covering all or most of what you want to do. You can buy an all day London Metro pass that counts as a rail ticket. There are two catches. First you must buy the pass at a rail station, not a tube station. Second, you must print vouchers. The info is here: https://www.daysoutguide.co.uk/uk-days-out The offer is designed for U.K. citizens, but tourists can use it. As the pass is more expensive than using an Oyster Card, you'll have to run the numbers to see if it's worth it.

http://www.tripadvisor.co.uk/Travel-g186338-c195600/London:United-Kingdom:2.4.1.Travelcards.Step.By.Step.html

They are very easy to use but you must have the right kind of ticket or pass.

My husband and I were in London for a week last September and we each bought a one week travel pass in paper, not on an Oyster Card. You need a passport-sized photo for this.

I printed out some vouchers online before the trip and brought them, but I did not correctly predict what we might want to do. Fortunately we found a booklet with vouchers at one of the train atations. We ended up getting 2 for 1 at the Churchill War Rooms, St. Paul's, and three or four others. Plus we were able to hop on a bus or ride the Tube whenever we wanted.

You have picked some pricy attractions--Hampton Court Palace is £19.50, Tower of London £24.50. I do not see Westminster Abbey in the book. Depending on how long you will be in London, it might be worth considering the one-week travel card.

I have used the Days Out 2 for 1 offers. Read the link that harelydonski posted, but in a nutshell, you need a train ticket TO and FROM London, or a 1 day or 7 day paper Travelcard purchased from a National Rail ticket office. Cards sold by Transport for London are not valid because the promotion is sponsored by National Rail to persuade people to travel by train.

If you are arriving at Gatwick, Luton, or Stansted airports rail tickets to and from London (you need to have purchased both directions, and carry both the used ticket and the future ticket) will qualify. Unfortunately Heathrow doesn't work.

We are arriving by Eurostar (which I know doesn't apply to this 2 for 1 deal) and we are flying out of Gatwick. It was my understanding that I had to have a travel card or train ticket stub of some kind for the same day as the attraction I am visiting. If that is the case, I wouldn't be able to use my train ticket to Gatwick for this promotion as we won't be doing any sight seeing on the same day as our flight. I hope I am wrong about that!
If I buy an applicable travel card, can I show it for multiple discounts, or is it only good for one?

It is good for multiple sights, on the day of travel only. I don't think it applies to Eurostar, check the fine print. But you can purchase a London day or multi-day railcard at St. Pancras as you exit Eurostar.

A Eurostar ticket does indeed not give entitlement to the 2FOR1 scheme. You will need a National Rail ticket - purchased from a rail station valid for the days you want the discount.

How long will you be in London?

A one-week Travelcard for Zones 1-2 costs £32.10 and can be used for as many 2-4-1 offers as you like during the period of validity. As I noted above, we went to 5 or 6. Plus you get the free transport around London. It could be well worth it even if you are not staying a full week.