Hi Iona,
In response to your question about sat nav apps, I have been using 'Waze' for the past year on my iPhone and have found it to be better than my old Tom Tom.
The app is easy to use, doesn't use up too much battery power on a normal journey. It also has a gasification element to add a little fun to your journeys but you don't have to use that if you don't need to. It has other features which pip the likes of Tom Tom.
If you need any more info feel free to ping me
Happy safe driving!
