Customer Profile

Relative to the average department store shopper, Debenhams’ customers are biased to women and the under 45s shopper and especially the 25-34 year olds. Its socio-economic skew is more to the C1s than the ABs compared to the other big chains M&S, John Lewis and House of Fraser. Regionally its relative strength lies with consumers in the North West and the North/Scotland.

http://academic.mintel.com/display/617127/?highlight=true#hit1

The grades

The classifications are based on the occupation of the head of the household.^[1]

Grade	Social class	Chief income earner's occupation
A	upper middle class	Higher managerial, administrative or professional
B	middle class	Intermediate managerial, administrative or professional
C1	lower middle class	Supervisory or clerical and junior managerial, administrative or professional
C2	skilled working class	Skilled manual workers
D	working class	Semi and unskilled manual workers
E	Those at the lowest levels of subsistence	Casual or lowest grade workers, pensioners and others who depend on the welfare state for their income

These grades are often grouped into ABC1 and C2DE and these are taken to equate to middle class and working class respectively. 
Only around 2% of the UK population is identified as upper class and this group is not included in the classification scheme. 

http://en.wikipedia.org/wiki/NRS_social_grade

Laura