Any idea how this is done? I want to get from Heathrow to Covent Garden using a pass of some sort. I have searched all the website for British Rail, 2 for one passes, and tube passes. None of them is clear about the above combination. When I try to make a purchase that sounds right the website tells me that I have entered information that cannot be processed. We arrive on a Thursday at 8:10PM and depart om a Wednesday at 5:30PM.
Transport For London (tfl) has lots of info regarding transportation. For the route you name, an Oyster card will take you via the Underground to all parts of London. It can be used for London travel while you are there, whether by bus or Underground ( Tube). The Oyster is available at the airport Underground station. More money can be loaded on the card as needed. TFL will have the details.
You cannot get a ticket at Heathrow that is good for the 2 for 1 deals. That's why you're not finding it - it doesn't exist.
See this page about the offers: http://www.tripadvisor.com/Travel-g186338-c195600/London:United-Kingdom:2.4.1.Travelcards.Step.By.Step.html
"Can I buy the Travelcard at Heathrow?
Heathrow is a tube stop; Travelcards eligible for the 2-4-1 deal are only available at National Rail Stations. You can purchase a single fare to London, and then purchase a Travelcard at a National Rail Station once you arrive in London. "
So, if you will be getting a 1 day or a 7 day Paper Travelcard to use the 2 for 1 deals, you will have to get from Heathrow to Covent Garden by another method, then buy your Travelcard at a rail station (not a tube station). Your Travelcard must be paper - not on a Oyster. There are also train tickets that are good for the 2 for 1 deals - but the Heathrow Express is explicitly excluded.
There are lots of ways to get from LHR to Covent Garden - the ways that make the most sense in your situation are tube via paper ticket (if that's truly the only ride you'll be taking outside of Travelcard), tube via Oyster (if you'll be taking other rides outside of your Travelcard), and minicab (what in New York is called a "car service" - a prebooked taxi, cheaper than getting a black cab at Heathrow). Or, you can take the Heathrow Express or Heathrow Connect trains to Paddington Station, where you can buy the paper Travelcard for your 2 for 1 offers, then take the tube (now covered) the rest of the way.
See this thread with a similar question for some more discussion: https://community.ricksteves.com/travel-forum/england/best-way-to-get-from-heathrow-to-london-and-purchase-7-day-2-4-1-travelcard-as-well
Thank you Harold. Your explanation is clear and is the first one that makes sense. Stuart