In Watching the English, Kate Fox gives a thorough explanation of how much she can pin down someone's social class by what they buy at Marks and Spencers (which is a department store that's branched out into groceries). I forget the exact details, but I think it was that doing a full food shop there made you upper-middle class, buying some food items there made you middle-middle class, and buying food items for special occasions there made you lower-middle class. Buying clothes from M&S makes you middle-middle class, and buying homewares makes you lower-middle class. The upper class don't shop at M&S at all, and the working class only buy clothes or homewares from there if they want something special. (I think - it was a while ago that I read it.) And that's just one shop.

Everywhere does social stratification, but nowhere does it like Britain.