Some months back I asked here for help finding an iPhone, speaking, navigating system, powered by CycleStreets.  Many people offered suggestions - for which many thanks.  I could not find anything which met the spec (unless I changed my phone to Android) but largely solved my problem by attaching my phone to the handlebars so I can navigate visually, but with a quick glance, rather than having to drag the phone out a pocket or the front bag. This works really well.

Recently George has drawn my attention to CityMapper which now has a speaking navigating system which George thinks is powered by CycleStreets.  I've got to try that.  George has also recommended cycle.travel which (I'm not sure) may not be available on a phone.  But on the computer it is excellent - rapidly responding to me tweaking the route.