Generally there are 4 or 5 major classes, all of which can be arranged in a spectrum..
Townie -- HipHopper -- Skater --Greebo -- Goth
There are some which don't fit easily anywhere on the spectrum such as Hippies, Meatheads, Geeks etc.
Basically, young people these days are sheep, and want to conform to the masses. People go along with a particular group, and share the same trends / styles, likes and disklikes.
Different areas of Britain have different proportions of each. Some places maybe townie dominated, whereas some may be myriad with skaters. Click on each one above to see what they are.