The posh look is probably wearing hunter boots which are certain brand of rubber boots for walking around in the countryside or maybe boat shoes. You would hear people referring to their parents as mummy and daddy not mum and dad but mummy and daddy especially the girls. People like Helena Bonham Carter might look a little bit scruffy and funny looking a bit mad because they don't really have anything to prove. Some very posh schools have secret initiation rituals that involve stupid things such as Bullingdon club where you can get smashed up by your fellow members. The image of hooligans who drink too much at fancy dress parties doesn't always go down well with non-posh people.