This is simple and can be done in 5 minutes using the steps below:
Please note that you do not need an eSIM supported phone. But your Watch3 must be the LTE version and not the Bluetooth version.
1: Install the Galaxy Wearable App on your phone from the App store.
2: Connect your phone and watch via Bluetooth.
3: Select ‘Mobile Plans’ on the App.
4: Select ‘Add Mobile Plan’.
5: Hit ‘Use Code’.
6: Scan the eSIM.net QR code from your phone.
7: Hit ‘Use Plan’.
8: Hit ‘Done’.
9: Your watch will receive an SMS with your UK number.