Class still informs much of British society. Look at the government front bench. Who you know rather what you know can still make a huge practical difference to people's lives – for example, think of the insidious growth of internships in this country. Lots of people, including many who are very influential, still think in terms of "people like us" even if they don't use those precise words. Many people feel that they validate their own social standing by looking down on others – not just Nancy Mitford's aristocrats casting a glance askance at fish knives and doilies, but also skilled workers looking down on unskilled workers and the attitude of high-powered professionals and business people to the "shop floor" workers, such as nurses, teachers and clerical workers. (Not all, of course.)
If you have some sort of grasp of how the class system works, you can play it to your advantage. You can also comprehensively undermine snobbery – which is great fun when you're bored.