Some small anecdoctal backing for the concerns I raised about the Scots langauge questions in the census - I discovered last night that my sister had left all four tick-boxes blank because she wasn't sure what Scots actually was, but her best guess was that it applied only to Doric speakers in the north-east. By any definition, she falls into the category of 'understanding' the language, and almost certainly 'speaking' and 'reading' it as well. It seems to me a much more high-profile public awareness campaign would have been in order to clear up the confusion - or even better, a brief clarification on the census form itself.
Note - I'm indebted to a comment someone left here a few months ago for the title of this post. I can't remember who it was, but thanks!