On Notes on a Scandal, why are those people wearig those silly crepe paper hats?

I haven't seen the movie so don't know for sure but I suspect it takes place in England & those are party hats from Christmas Crackers. That is a fancy wrapped little cylander which pops when you pull it open. They usually have 1 or 2 tiny candies inside along with a crepe paper hat & a horn or whistle of some sort. They may look silly at the party but they are a lot of fun, maybe just seeing how silly those things look on everyone....but fun none the less.