Restoring from iPhone backup.

Hello there, alanptk.

It sounds like you are unable to select an iCloud backup to restore your new iPhone 6. The following Knowledge Base article outlines the possible reasons this could happen:

If you need help restoring from an iCloud backup - Apple Support

I can’t select an iCloud backup

There are several reasons that there might not be any available iCloud backups for your iOS device:

• You have never successfully made an iCloud backup of your device. Check instructions for making backups in iCloud.
• Your device has an earlier version of iOS than what you used when you made the backup. Learn what to do.
• Your iCloud backup might have been created with a different Apple ID.
• You haven’t backed up in 180 days. If you haven't backed up your iOS device to iCloud for 180 days or longer, Apple reserves the right to delete the backups associated with that device. Review the iCloud Terms and Conditions for more information.

In your case, you may likely be seeing the second issue: Your new iPhone 6 has an earlier version of iOS than your backup. The referenced article provides the steps to follow to get your iPhone 6 updated:

Set up, update, and erase your device

1. In iTunes, or from the Set Up screen on your iPhone, tap Set Up as New instead of Restore from Backup. If you already tapped Restore from Backup,tap Back to return to the Set Up screen.
   
2. Follow the remaining steps. For now, you can skip the steps for Apple ID, Touch ID, and passcode.
3. Once the set up is complete, update your device to the latest version of iOS.
4. Let the update finish, and wait for your device to restart.
5. Erase your iOS device: Tap Settings > General > Reset > Erase All Content and Settings. After your device is erased, it restarts and you'll see the Hello screen in the Setup Assistant.
   

Now you should be able to set up your device again, and select a backup to restore from.

Thanks for participating in Apple Support Communities.

Cheers.

Hello again, alanptk.

You are very welcome. I'm glad the information helped you resolve your issue.

Sincerely.