Nancy R:
I meant to buy Zone 6, not higher. They must have added more Zones since I was last there in 2011. But buy these things ahead of time online, not when you get there! Much more convenient and you can use it right away.
I believe up to Zone 9 is the trains. Heathrow is in Zone 6 and for most of London you only need up to Zone 2 including the O2, excepting Wimbledon or Kew Gardens, which would be Zone 3. The good news is that they have extended the hours for the tube at nights, I recently heard. That's really good, because they used to close early 11-12 ish PM. You could get stranded far from your hotel, and wind up having to take a long cab ride I've also got caught with the trains on Sundays, with some stations closed, and having no one to help you figure out how to get the correct ticket from a machine, or figure out when the last train returns (could be earlier than you think) Have learned the hard way, to get them in advance and I'm pretty sure they don't sell them on the trains, like they do here. http://i.imgur.com/JPKI5ZA.gif Here's the map with the Zones and trains. I been going to visit, and have friends in various places, for the last 6 years at least 2-4 times a year. I'm just starting to drive, but you really don't need to at all. It's also very easy to take side trips to Paris by high spped train thru the Chunnel and short hops by plane, bus or ferry ( a few hours to Holland) everything is pretty close really, took a plane to Italy 1 1/2 hours, Portugal 2hours. All inexpensive, maybe around $100 RT if you shop around.