As well as savouring the expansion of the normal Sky Go service with a further 14 channels, as announced today, Sky viewers are being offered 50 per cent off the Sky Go Extra subscription fee for 12 months. And you won't even have to sign a new contract.

Sky Go Extra enhances the Sky Go experience, particularly for mobile devices. Not only does it double a user's device allowance from two devices permitted on an account to four, but it also opens up the download and offline viewing options.

General Sky Go, which is free to use for all Sky TV customers, allows viewers to watch live, catch-up or on-demand content from a host of TV channels, which are all available from today. They include all of Sky's own stations and those of Channel 4, plus Comedy Central, MTV, Dave, Watch, Gold, Discovery, Nat Geo, History, Alibi, Nat Geo Wild, TLC, Animal Planet, Good Food and Eden, with  57 channels now in the line-up.

Sky Go Extra usually costs an extra £5 a month to download the content rather than watch it streamed over Wi-Fi, 3G or 4G. At present, you have to pay only £2.50 a month for the first 12 months if you upgrade now.  But you must be a Sky TV customer.

Sky Go is available for Android devices, iPhone, iPod touch, iPad, PC and Mac. It is also available on Xbox 360 but without Sky Go Extra (as the console is hardly mobile).

Find out more about the reduced subscription price at sky.com.