I know little of the Cambridge University study, Gromit and can only speak from my own experiences.
I did not as a child and do not now move in particularly exalted circles. However, I do come across many people from all walks of life in some of the work that I currently do. I can say quite confidently that it is extremely rare to encounter anybody over the age of about 50 who cannot read and write reasonably competently. However, the number of people I meet aged under about 30 who lack such basic skills is alarming to say the least.
If you can, do an admittedly unscientific straw poll yourself to see what I mean. If you believe that primary school standards (by which I mean basic results � teaching children to read, write and add up) are better today than fifty years ago, we must be living in different countries.