1. Make sure you have completed the basic Xbox 360 Setup.
2. Change your system locale to "United States" in System Settings
3. Register for a Free (silver) Xbox Live account and set your Country to United States.
4. Go to Apps. Voila, you have many new apps to download!
5. Download the apps you want. When you are done, log out of your US account and log back to your old Xbox Live Gold account to start watching.
For UK based apps, register an account with Country set to United Kingdom
Note: Some apps require a US/UK IP address to download, please refer to Downloading website apps onto your Xbox 360 for more information.
Available apps from a US Xbox Live account. (from the time image was taken )