If you download Here it alsocovers public transport in major cities, and outside in some places too.
Download the map you need using WiFi and you are good to go, you do not need data.

http://www.imore.com/nokia-launches-...phone-and-ipad

Also available for Android.

Well, it makes much more sense when you explain the situation while annoyed with me than it did at the beginning. So, at risk of annoying you again, I have another suggestion.

Watch this little video to the end, about the Knopf Mapguides, the most wonderful little books, divided into folding-out small maps, 8 in the case of London, with attractions and all sorts of things marked clearly and also some text but not too much. I have a bunch of them now, very lightweight & fit perfectly in a pocket.

Watch this: http://knopfdoubleday.com/knopf-mapguides/

I'll make you a bet, dominiquejade, buy one and carry it along with your phone. I bet you'll use the Mapguide more. About $10 on Amazon.

I forgot to mention, there's also a tube map at the end. Everything a girl (me) could ask for.

this map guide you mention sounds like a good alternative, as it solves the problem of not being able to relate attractions, streets, etc. to the tube system, which was my initial concern.

It is, indeed, a good alternative. It shows you where everything is on a map, including ones we aren't aware of. Each section is a walkable part of the city, so if you have a destination in mind, you can also see what's nearby. I think you'll do well to have one and so inexpensive, you can't go wrong. I carry one, even in cities I know. We never know all there is to see and these lovely little books fill in the gaps without extraneous text & weight.