There's a lot of ambiguity about population - it all depends on what you think "Chippenham" is.
At the 2001 census Chippenham CP had a pop'n of 28,065 Census 2001, Chippenham CP Headcount
If you include Chippenham Without CP and Langley Burrell Without CP, which some might, but this includes the population of a few surrounding villages, then you'd have a total of 33,832
Chippenham Town Council estimate the population to be "over 40,000"
Someone put a figure of 33,189 in the article, again quoting from the 2001 Census, but I can't equate this to the data available.
I put an approximate figure of "30,000" in the infobox based on the 2001 census data

What is the "right" figure to use?