Method of demographic research

This i show i have been gathering my demographic research. (I hope its the right way...)
First of all i used acorn http://www.caci.co.uk/acorn/. I downloaded their acorn classifications pdf. This document classes every type of hierarchy in the country from wealthy achievers to hard pressed. It categorizes people. So therefore what i had to do is find out the average income for my target audience (doctors, nurses etc) and categorize them. Once i knew what categories they are in i could search the site for the demographic details on everyone one who's in that category.
http://www.caci.co.uk/acorn/acornmap.asp - Acorns classifications
Incomes:
Teachers income - http://www.teachuk.com.au/salaries.html - £28 931 OR £31 178 in London Area.
Nurses Income - http://news.bbc.co.uk/1/hi/uk/4860358.stm - £28,400
Doctors Income - http://www.nhscareers.nhs.uk/details/Default.aspx?Id=553 - between £34,584 and £64,632