O2 has confirmed, via Twitter, that the Windows Phone 7.8 update will be coming to Windows Phone 7.5 users by the end of January and available via the Zune service.

The surprise comment comes ahead of an official announcement from Microsoft, Nokia, HTC or any of the Windows Phone handset makers.

O2 stocks several of the previous Windows Phone 7 devices such as the Nokia Lumia 800 and Lumia 900.

Windows Phone 7.8 promises to bridge the gap between Windows Phone 7.5 and Windows 8, acting as a piecemeal arrangement after Microsoft confirmed that those on Windows Phone 7 wouldn't be able to upgrade to the new, more powerful Windows Phone 8.

Windows Phone 7.8 brings a number of new features to the operating system, including the new Windows Phone 8 start screen with adjustable tile sizes.