At first I thought it was just a way to say costumes for Halloween. But no, the British love their fancy dress parties. There are multiple clubs where each week there is a different theme to dress up for. Almost all the Christmas and New Years parties were costume parties as well, each having their own theme.
To top it off, I had a few friends that had their birthday on the same day and decided to throw a joint birthday party. In it they asked people to dress as something that started with "A" or "K" (their names). I wasn't sure how many people were going to show up in costume so I didn't know how elaborate to make mine. (not to mention time or money) I finally went with being a King when I found a Burger King and got a crown. I bought a sword that I could blow bubbles with and a "Santa's bag" on clearance that I cut open and glued a white scarf around the fringe for my robes. (For a total of £2.50 from the pound store). About half the people were dressed up so I spent about the right amount of work.