I assume you are trying to get US Netflix content in the UK? I don't think that is device-locked, but region-via-ISP locked.
It doesn't matter what region your device was manufactured for, but from where you are streaming Netflix.
Unless it works some way other than I understand. well, look at this this way: I carried my made-for-USA Surface to Latvia some years back and during the 3am sleepless jet lag nights, watched Netflix. My own account was now accessing Latvia/EU market content. Not US (so I was getting things like CBS all access programming and shows like Fargo, which US Netflix customers do not have).
...now, this was through my browser, and not through a Netflix app. If it works differently through an embedded TV app, I wouldn't know, but I doubt it does.