If you want it guaranteed hidef on demand, torrents are the way to go for sure.
There are a whole bunch of websites dedicated to streaming shows and movies. Most of the time you just have to type in the name of the show/episode and "streaming" and google will give you great links. That being said, you will have to close a few pop-ups and sometimes the stream will be slow, but there will usually be numerous options.
I just installed a £10 Sky Now Tv box. A £4.99 entertainment pass gives me Sky 1, Sky Atlantic, loads of catchup TV and it's all rather easy. Requires Overplay Smart DNS or similar to fool the box into thinking its in the Uk. Works a treat. Not yet commenced my free 30 days of Sky Movies..
Game of Thrones looks great on it.