I have found some conflicting information about trains within London. We are considering a stay in a serviced flat near Canary Wharf. We understand it is not close to the main attractions and will require trains to get to/from. However, the price is unbeatable and the flat is all we want: modern, comfortable and relatively spacious for a family of 4. There is a London Tube station around (20 min walking according to Google Maps) called Canary Wharf. However, there is another much closer, almost across the street, station labelled "Docklands Light Rail". Some sites I read discuss only the Tube, the Overground and buses. What is this Docklands Light Rail? How much does it cost to ride it? Is it open at evenings and weekends? I'm planning to buy Oyster cards to use the Tube, what card should I buy to use these Dockland Light Rail trains?
Docklands Light Raiway is fully integrated with the underground from a fare point of view and has a number of connection points with the underground, overground and national rail. It runs 7 days a week, construction work excepted. Capacity was beefed up for the Games.
Just adding to Marco's comment, you Oyster card will work fine on the Docklands Light Rail (generally referred to as "the DLR"). If you go to the Transport For London website (tfl.gov.uk), you'll see the DLR identified on the tube maps. You can use the journey planner to check the schedule and see how late it runs to your location.
http://www.tfl.gov.uk/modalpages/2632.aspx, http://www.tfl.gov.uk/modalpages/2625.aspx All you need to know. Remember to purchase the 2 for 1 deals http://www.nationalrail.co.uk/times_fares/promotions/two-for-one-london.html
at the either Paddington, Victoria or Waterloo. Good way to save money. Just remember virtually all museums are free. Pricey spots are the Tower of London, St Paul's and Westminster Abbey. However, you can see the interiors of the latter two free by attending evensong. Enjoy London. GREAT city!
The DLR moves a bit more slowly, but it's easy and reliable, and fairly quick to connect to the underground, depending on your station. It's easy enough to get to Bank or Tower Hill, and switch. Or, Canary Wharf, etc. Not knowing your station, can't say what zone you'll be in, but that's the only thing that will drive your cost up. I'd avoid peak times for commuters, but would say that of the whole system.
The Jubilee Line Canary Wharf station will take you directly into the West End. Use the DLR for the City of London or to get to Greenwich.
Be prepared for some good news. All of the Isle of Dogs, Canary Wharf area, all of the DLR as far east as East India Docks, is all in Zone 2. That means that it is no more expensive to get around than central London. The DLR trains take a bit of getting used to as they are elevated so that you have to go up to them at most stations. The trains are short driverless ones, all controlled by an electronic brain. Stops are frequent and the DLR is best used for "last mile" type of transit, changing to the much faster Jubilee Line (Extension) for runs to the West End. If you are at (you haven't said) Heron Quays it is walking distance to Canary Wharf.
We will be staying within a 3min walk or less from South Quay Docklands Light Railway Station. I still can't believe how lucky I am for getting such a discounted deal on accommodation there.