The pattern details for the Original Granny Ripple and details on how to square off the ends and prepare for an edging is now for sale on Ravelry – http://www.ravelry.com/patterns/library/soft-granny-ripple.
I have also made a more symmetrical version of the ripple that is really what I was after the first time! Pattern for that to be available when I have finished the blanket.
I have also given fairly detailed notes of how I made the Spectrum version for anyone who might like to copy it. (See link below)
More views of the blanket. Edging not included in pattern.