Well, I've installed it and it seems to work. I've got the benefit (?) of the premium version for a few days but I don't expect to use it in earnest before that runs out. I don't need the app at all while on the island and I'm not planning to go anywhere else soon. I can always add things later if I want to. My mobile is a Galaxy Y because it's smaller for the pocket so that means the screen isn't huge. It will be interesting to see how it goes with my slowly ageing eyes (or perhaps my arms are just too short). I imagine that the installed POIs will disappear when the premium service lapses so I'll have to find/choose a source of POIs to replace them. Learning to work the app will probably take me a while if I'm not actually using it in anger for now.... Thank you for your help, papabravowhiskey.