Hello Pontefractcake,
Did you also take the steps below before starting the transfer process?
• On your Android device, make sure that Wi-Fi is turned on.
• Plug your new iOS device and your Android device into power.
• Make sure that the content you're moving, including what's on your external Micro SD card, will fit on your new iOS device
• If you want to transfer your Chrome bookmarks, update to the latest version of Chrome on your Android device.
You can also find those steps at the beginning of this article: Move from Android to iPhone, iPad, or iPod touch - Apple Support
The additional recommendations at the end of the article may also help with that process:
• Make sure that you leave both devices alone until the transfer finishes. For example, on your Android device, the Move to iOS app should stay onscreen the whole time. If you use another app or get a phone call on your Android before the transfer finishes, your content won't transfer.
• On your Android device, turn off apps or settings that might affect your Wi-Fi connection, like the Sprint Connections Optimizer or the Smart Network Switch. Then find Wi-Fi in Settings, touch and hold each known network, and forget the network. Then try the transfer again.
• Restart both of your devices and try again.
• On your Android device, turn off your cellular data connection. Then try the transfer again.
Should you still face difficulties with moving your data over, you'll want to reach out to Apple Support so they can look into this further: Contact - Official Apple Support
Take care.