I received an email from Carphone Warehouse on Christmas Day saying I could choose from one of the three films for free on Google Play as a Christmas present.
I clicked on the link in the email and it took me to their website, then linked through to the Google Play store where it let me have a movie free. I clicked on all 3 and it added them all to my Google Play library.
I have no idea of the criteria to have received this email. I bought a Galaxy Fame from them in February this year and a phone charger in April time, so spent around £65 with them. If you know any more details please feel free to amend this - definitely worth checking your emails for it though.