You can create a new Apple ID to access the UK App Store from any country following these steps:
- Go to https://appleid.apple.com/
- At the bottom of the page, click on the country flag.
- Choose UK.
- Once you are back at the main page, verify that you now have the UK flag at the bottom of the page and then click on "Create your Apple ID".
- Enter all requested informations using a different email address than the one you actually use for your Apple ID.
- Confirm your email address.
Once your new UK Apple ID is created, you will need to activate it for the App Store on an Apple device before you can use it on your Apple TV.
To activate your new UK Apple ID for the US App Store on a Mac, follow these steps:
- Open the App Store on your Mac.
- Logout from your current Apple ID Account.
- Sign In with the new UK Apple ID you created.
- You will be asked for a payment method, you can just choose NONE and enter any valid address from the UK and any UK phone number.
Once your UK Apple ID have been activated for the UK App Store, you can switch between the two accounts on your Apple TV, iPad or iPhone to be able to access both your current country App Store and the UK App Store.