Firstly Durham is great and you'll love your time there im sure. it depends on what societies and events youre looking to go to, or join. However, i would say a dinner jacket is a must and yes, you would stick out without one. But i wouldnt worry too much about it, people dont really care. I quite often buy cheap dinner jackets and shirts and get the trashed on nights out or lose them. I pick them up cheaply and dont worry if they get ruined on a night out as the black tie events are usually fairly boozy.
From my experience i might have many 5 black tie events/ balls a year that i would go to. somepeople might not go to any though.
most people would wear a standard tuxedo, however lots of people will be in smokers jackets or velvet dinner jackets. The odd scot might wear a kilt. it vaires