Opening the boot from the outside also unlocks the car - as per a post I have seen.
I have put a fresh button cell in the keyfob, just in case a flat battery caused this issue.
My plan for the locked-in situation is below, with escalating steps:
1. Place keyfob, with buttons facing up, in central storage.
2. Attempt to power down the car from infotainment panel.
3. Use the Bluetooth key in the iSmart app to unlock and start car.
4. Call AA for help and get a family member to bring the spare key.
5. When help arrives, ask them to first try and open the boot from the outside.
6. If spare key is available, to open the driver's door with the manual key. We have practiced doing this. I suggest all owners should get confident in doing this.
7. If no spare key is available, or if an emergency exit is needed, to crawl into the boot and open from the inside.
8. If nothing works, to open the bonnet and get AA to disconnect and reconnect the 12V battery.
9. Pray!
Edit: Added trying the Bluetooth key.