What should I pack for a Fall semester in Wales?

I am going to Swansea Wales from September to middle of September for studying abroad, (I'm from Chicago, IL ) . I am a horrible packer and really want to bring everything, but I know I can't, especially all of my shoes. So, what do you think I should pack? Do I need a heavy jacket? A lot of dresses? Also, do Welshmen find American accents y? Just wondering. Thanks :)