Some basic questions remain the same: full name, sex, age, relationship to head of family, occupation and the like. Supplementary questions change. 2001, for example, was the first census to ask for ethnic origin. It caused quite an outcry because we were allowed to be Scottish, Welsh, British or Other, but not English. I went in as "Other - please specify" and "English".
Ewood, that is so annoying. I remember seeing a documentary about a pub who had a St George's Day Celebration and were taken to court for being racist...