If you create a folder called Uploads in your OneDrive's Geowigo folder, and then start the app on your old phone, the app will upload your savegames to this place.
Then you just have to move the savegames you need to the parent folder, "Geowigo".
They will be downloaded alongside the cartridge files when you run the app on your new phone.
Thanks, I will use this in the future In the end I took a borrowed Android phone with me and did 'I Love Vienna' using Whereyougo without any issues, the other one I had previously saved I just started again (I'd only done one zone and it was close to another cache) but had to give up anyway after about an hour's play when I couldn't find a hidden zone...