Update: Royal mail have confirmed that the stamps will also be issued in sheets self-adhesive and printed by De La Rue.
From the Royal Mail press release:
300 DAYS TO GO - ROYAL MAIL DEFINITIVE STAMPS MARKING LONDON 2012 OLYMPIC AND PARALYMPIC GAMES HIT THE PRESSES
“People sending letters to friends or family in the UK and overseas tourists sending mail abroad will be able to commemorate this historic event by using these stamps to post their items. As we reach the 300 day countdown, it’s exciting to see millions of these stamps rolling off the printing presses.”
The stamps will be available from all 11,800 Post Office branches across the UK from Thursday 5th January 2012. There are four new stamps - two 1st Class and two for Worldwide use to post items up to 20 gm in weight. Both sets of values feature one stamp with the London 2012 Olympic Games logo and one with London 2012 Paralympic Games logo.
Around a million stamps an hour in striking orange and blue inks will be printed on specialist stamp printing presses in Walsall, West Midlands over the next few days.
More images of the booklet, production, and checking:
Although appearing red in these images, the stamps will be orange - or maybe the same colour as the 1st class 'flame' that came before the gold, and with which we are so familiar. It also shows that on the web, they appear to be printed only 'two-up'.
There's a film of printing and interviews on Stamp Magazine's website.