As usual, I'm of two (or three or four) minds. And before I even start in on that, it should be noted that Hodder will continue to publish the original versions as well. So there's no danger of 'jolly japes' being lost to us forever.
So. On the one hand, I understand the changes being made to make the books a bit less offensive. On the other, I've always felt weird about the changes made to P.L. Travers' amazingly offensive 'Bad Tuesday' chapter in Mary Poppins.
And on the other one hand, I understand changing the books to make them more palatable to a new generation of readers -- turning more children on to reading, hopefully raising literacy rates (and, for Hodder, selling more books) -- but on the other other hand, some of the proposed changes seem to be less about modern translation and more about simple dumbing down, like "it's all very peculiar" to "it's all very strange".
I've never been on the Blyton train anyway, so... eh. It isn't one that I find myself getting worked up about. If something similar was done with E. Nesbit's books, though, my head might explode.