I'm from the UK and you pretty much never hear anyone say 'soda' or 'pop'. It's a dead giveaway if you do that you're not from the UK or are fairly old. I've noticed that older people tend to say 'pop' when they are talking to children. Coke is used to refer to anything cola flavoured, be it Pepsi or Coca-Cola or any other drink with a cola flavour. We then tend to refer to other fizzy drinks by their respective name. e.g. Lemonade, cherryade etc.