Just a quick post to see if anyone finds this useful.
You can cache large areas on Google maps using WIFI (or when you have data) so you can navigate in areas with no phone signal easily. This is particularly useful for use abroad when the data costs are high (you can cache other countries before you go there then delete the cache afterwards).
I have found this very useful when in the lake-peak district, most of Wales and north Norfolk where I know there is poor or non existent signal for all networks. An area 50 miles square is about 50-70 meg in the UK so all of the UK can be cached fairly easily on a small sized SD card. Great for emergencies too or when you run out of credit.
One thing to bare in mind is that this is a snapshot of the time when you cached the maps so make sure you update at least once a year in case the road systems change.
Hope this helps someone.
DZ.