I found the answer on a Sony forum, worked perfectly. Follow this:
1. Hit the "Home" button on the Sony TV remote. You'll see a bunch of icons popup
2. Arrow down to the bottom to Settings (it looks like a gear icon on the x900e)
3. Once in settings, go into External Inputs
4. Scroll down and go into HDMI signal Format (Enhance 4K HDMI signal Format)
5. Once there you'll see the magic setting we need, which is the Enhanced Format (Displays High-Quality HDMI signals on HDMI inputs 2 & 3...), so select it and navigate back out using the back button
I then went in and switched my apple TV to HDMI input 2, unplugged its power and replugged it back in. When the Apple TV booted back up, I went into the display settings and it showed as being HRD now...wooohoooo!!!! So yeah, it apparently only works for inputs 2 & 3 so be weary of that.
Paul