annoyingly I'm at work and can't really confirm this, but just got press release saying:
NEW ALBUM “THE KING OF LIMBS” IS NOW AVAILABLE TO DOWNLOAD AND A NEW VIDEO IS RELEASED
Radiohead have brought forward the digital release of their new album “The King Of Limbs” by 24 hours with the album now being sent to those who pre-ordered it earlier this week. It is also available for new orders through www.radiohead.com at a fixed price of £6. A special edition is also available.
With everything ready on their website, the band decided to bring forward the release by a day rather than wait until the planned date of Saturday, Feb 19 to deliver the music.