This site has started some discussion on a Tripadvisor Forum. See Here
Nice to see some people looking at the site. Just to confirm – this site uses Census 2006 data mainly but is in no way connected with the CSO.
The compilation of the best and worst towns was carried out using certain data from the census . There are probably many other statistics that could be used to get a fuller more accurate picture- (if they were available) – but the census data was all that was used.
The chart is probably more of a measure of the wealth or affluence of a town rather than trying to be an accurate measure of the quality of life in these towns.