Are grade boundaries decided on the basis of how well people do, or are they just independently set based on how hard the exam is? If it's the latter, they should be decided before people sit the exam and no changes can be made afterwards, therefore people know that what they're getting is what they get - there's been no meddling at the last minute.
If Ofqual and all the exam boards want fewer people getting good grades, why don't they pull their trousers up and make exams harder, rather than making it the fault of the pupils - "too many pupils got C grades because grade boundaries are slack", NO, "we didn't make the exams hard enough so it's too easy for students to get C grades" - that's the awful thing is that it's their fault but there's a definite hint of blaming students for doing well rather than admitting their own failings in some of the newspaper articles.
(I'm not saying it is easy for students to get C grades, but if they want fewer people getting Cs and above, surely what you do is you wait until the next set of exams and you make the papers harder, rather than thinking "ooh, people sat their exams a couple of weeks ago, we'll tighten those grade boundaries and Joe Public will think it's wonderful that the rate of GCSE passes are going down!" )