Take a look at Google Play. I've bought movies on my phone and streamed them via Chromecast to a TV and they were fine (only a 20" TV, haven't tested it on a larger one). Also offline/online tablet watching.
Amazon don't just do packages. You can also rent films (not sure if you can without the package).
There's also Wuaki, but their terms aren't as good as Google. You only get the film for 2 days, where Google give you 30 days to watch, and then you have to watch within 2 days. And their "buy" are actually "rent for 3 years".
Sky store is fine, but the range is quite limited.
There's also Knowhow, who I haven't tried on principle as it's run by Dixons/Currys.
And if you like arthouse stuff, there's Curzon Home Cinema, although I'm personally impressed with the range on Blinkbox.