Just to clarify--you don't need a pass to use a subway in London--a subway in the UK is an underground pedestrian walkway, usually running under really busy streets. The "subway" is called the Tube or the Underground and you will want to use those terms when doing research.

There are numerous (to put it lightly) threads here on the Oyster vs. the 7 Day Travel Card. If you put those words in the search box you can read other posts. I believe there is a new "complication" in a requirement of a photo to purchase the travel card.

The Oyster card is just a plastic means to carry credit for travel. You will load it with some amount of cash (called PAYG--pay as you go--)or buy the "value" of a travel card. The PAYG method has a set cap for how much will be charged per day and the card can be topped up if you mis-calculate and need more credit on the card. If you want to turn it back in at the end of your trip, you will be refunded whatever value is left. You can purchase such at LHR, if you are arriving at Heathrow and want to travel via Tube. (which is a good but not only option)

You can also put the "value" of a 7 day travel card on the plastic Oyster card. In some cases this will end up being cheaper than PAYG for same time frame.

You can also go to a RAIL station and purchase a PAPER 7 day travel card. These cost the same as if you "loaded" such on an Oyster card. These are the things that make the 2for1 vouchers usable.

Must sees? OH, my, you may get blasted for asking such an open ended question. What do YOU want to see? Have you done any research yourself to make a possible list? But I'll say the Tower and the British Museum plus about 20 others of my preference!

Are your 7 days really 7 days IN London? Are you counting arrival and departure? If so, you may only really have 5 "good" days and you say you've already planned half of those with tours/day trips? That doesn't leave much time so you need to pick a few things you are interested in.

Get familiar with a map NOW. London's hugely spread out and "must sees" will tend to be all over the map. Travel takes time.

Have fun finishing up your plans and a great trip!
(you can also look at other people's trip reports for ideas, too--if you click on my screen name, I have 3 trip reports of times in London that might interest you.)

London Walks is a great company. Just show up at the stated time/place, pay and go. They also have Explorer days which are day-long excursions to out of town places such as Stonehenge, Greenwich, Bath, Cambridge, Cotswolds, etc. Over the years we have taken at least 30 of their walks, and only one was disappointing. When we were there recently, we took (for the second time) the Jack the Ripper walk. It wasn't nearly as good as a few years back. Most of the original sites are now modern buildings, little-to-no atmosphere, huge number of people on the walk. It amounts to a lecture about the events while walking through the suburbs.

Last time we were there we used Oyster card but I really can't compare the two.

Help with tavelcards, oyster cards, 2 for 1's:
http://www.tripadvisor.co.uk/Travel-g186338-c133479/London:United-Kingdom:Paper.And.Oyster.Travelcards.2.4.1.Offers.html

London Walks www.walks.com have an excellent reputation and their walks are great. We have done about 12 over the years. The guides are always interesting and are sometimes actors which adds a bit of flavour.

The good thing about not prebooking is you can check the weather first, or see if your feet still hurt from all the walking the day before or if you are ill you can go the day after.

In the UK a subway is, as texasbookworm says, an underground pass to get across a busy road. Or it's the name of a place you buy a filled roll for lunch. It's the tube or Underground, mostly the tube. The maps and other info on www.tfl.gov.uk are well worth studying before you leave home.

Kay

For your time period, a 7-day travelcard makes sense, whether you get a paper one or one on Oyster. If you're travelling in from Heathrow, then you can get one on Oyster for zones 1&2, with the add-ons for travelling to and from Heathrow; if you want the paper one to take advantage of the 2for1s, you'll need to buy just the single fares to and from Heathrow, and get to a National Rail station as soon as you're in central London.

Don't forget that your travelcard will also cover buses, which you may find as useful as the tube, depending on what journeys you want to do:
http://www.tfl.gov.uk/gettingaround/15101.aspx

For your time period, a 7-day travelcard makes sense, whether you get a paper one or one on Oyster. If you're travelling in from Heathrow, then you can get one on Oyster for zones 1&2, with the add-ons for travelling to and from Heathrow; if you want the paper one to take advantage of the 2for1s, you'll need to buy just the single fares to and from Heathrow, and get to a National Rail station as soon as you're in central London.>>

any chance that Boris will sort out this nonsense so that there is one unified system?

no, thought not.

Thank you to everyone who posted a response. I got the message that it is the "tube" not the subway (sorry). I have done a bit more research and understand a little better what the the Oyster Card is versus the Travel Card issue. It sounds like it will be close to a "toss up" for our schedule if we should purchase the 7 day travel card or not. Having the travel card loaded on Oyster appears to be the most convenient method even if it turns out to be a little more expensive than pay as you go as we may take a cab from time to time. It may come down to whether or not we want to use the 2for1 offers. We are checking those out now. Again, thanks everyone and I am checking some of the trip reports that have been posted. Regards, eplus

>>any chance that Boris will sort out this nonsense so that there is one unified system?<<

It's a promotional scheme for the national rail companies aimed largely at their commuters who live outside London, not a primary part of the London-wide transport system: so even if it got anywhere near the top of his priorities list (and how many votes would there be in it?), I can imagine their reply.

any chance that Boris will sort out this nonsense so that there is one unified system?

This has nothing to do with anything Boris is responsible for. And if for some reason he does decide to put pressure on the TOCs the likely effect is the WITHDRAWAL of the loophole and for it to become exclusively for train travel to London from outside London*


* for London 2-4-1s.

I am confused about which train stations belong to the national rail system.
Does anyone know if the Gatwick Express Train from gatwick to London Victoria Station qualifies for the 2 for 1?

Sorry for this short hi-jack of the thread, but..does anyone know about 4 people traveling on the Gatwick Express for the cost of 2?

Many thanks!

The answer is yes....if you buy a return (round trip) ticket either on the Gatwick Express or the slightly slower but cheaper reguar train from Gatwick to Victoria. At that point, with the return ticket, you have qualified for all the 2 for 1's we are discussing here and can use the much more flexible oyster card system either PAYG or a 7 day travelcard with some PAYG for extensions (6 days or more 7 day travelcard, 4 days or less PAYG,5 days you can go either way!