You must stop if requested to do so by a police officer, but there is no legal obligation to answer any census questions put to you by a civilian. This means it perfectly legal to drive into the census area, tell the person with a clipboard you don't wish to answer any questions and leave.
Absolutely right.
Its far more fun to pull in and pretend to be from another Planet/Country and/or just give absurd answers.....

If I'm in a rush, I'll pull in as directed by the Copper, tell the Census taker, politely,to ask somebody else and leave.