If liked the look of the Chromecast (have a nose at my overview here) and went out and bought one from your local electronics retailer (Currys / PC World in other words), then you should definitely be heading to https://cast.google.com/chromecast/offers/ to grab your free £4.99 of credit to spend on a movie.
Hey, it’s the Easter weekend. Get yourself a beer and watch a free film. Not bad huh ? Especially if it’s raining and you want to keep the kids entertained.
You have to buy and redeem the offer before July 15th, so you’ve still got plenty of time.
Note, although it states that this is only for movies, it looks like you can buy anything in the Play Store.