@nigeF: Sadly you may only transfer content from a non-Galaxy phone to a Galaxy phone with Smart Switch, as it does not work the other way around. What I'd suggest is backing up your personal data to your Google account via Settings > Accounts and Backup > Backup and Restore > Google Account, and backing up your data from here. Now, when registered to another Android device, this should automatically sync with your backed up data, although please be aware the data will be limited to the backup options on the account itself.
one plus have their own version of smart switching... think its called Oneplus Switch even, its on the google playstore if you want to check it out.
