there. You can use the Oyster card on the underground, surface buses, and even the river boats. The Tube is really easy to navigate - especially with Google maps, and minding the gap is part of the whole London experience. And the Picadilly line goes to the airport, so you can take it from the beginning.

Just be careful because you can't use the Oyster card for some surface trains that go outside of London, so be aware of that. I thought you could and ended up riding a train to Windsor Castle that I didn't have a ticket for and had to pay for the round trip ticket when I boarded to ride back to London because I couldn't get in with the Oyster card.

There are lots of must-see's in London if you haven't been there before. Buckingham palace, Westminster Abby, Parliament, Tower of London, Harrods, British Museum, etc. Can't really go wrong with any of these if it's your first time.

For Heathrow flights, you typically do want to get there a bit earlier than normal. Seems like everything takes a long time - even connecting flights.