Last week I bought an LG TV and a Chromecast from my local Tesco. The TV was reduced from £370 to £299.
Plugged the Chromecast into one of the HDMI slots on the back of the TV and then set it up using my Nexus 7. Just download the Chromecast app from the Play Store and follow the instructions. Only takes about 5 minutes to complete.
There seem to be 2 ways to cast (stream) items to the TV. Most apps (i.e. Youtube) have their own "Cast" tab. Just select that and play the video. Using the Chromecast app you can cast the tablet screen to the TV and play a game for instance. However I did find some lag when playing a fast moving racing game.
Couple of tips.....
Make sure your WiFi signal is good because the Chromecast connects to your home network.
A short HDMI extension cable is supplied but you may need a longer one. This is because the Chromecast sits at the rear of your TV which is a bit of a WiFi shield, so you might need to move it to the side to get the signal.
Hope this helps