Sadly I would guess he'll just take this as a sign that he needs to cut harder and cut faster, and as usual a large section of the press that cares more about the ideology of austerity than the economics of it will lap it up.
I just don't understand how it isn't blatantly obvious to the whole world that the credits-rating industry, at least as far as whole countries go, is pretty much a massive racket - not after Greece was given a triple-A rating even as the country was rapidly, and not even very secretly, going bankrupt. Or, in the most generous case, if not a racket then at least nothing like the precise science it's made out to be.
Perhaps it's one of those cases where everyone knows in their heart of hearts that it's a load of bollocks, but carries on treating it as gospel truth because that's easier than tackling the shared delusion.
At ECGD there's a whole division devoted to analysing credit ratings and trying to predict how they'll change a few months or a year down the line. The Greece debacle makes me think they might as well be consulting Mystic Meg's horoscope page. And the companies that publish these ratings make an absolute fortune...