The Bangers were known for their appallingly awful Quidditch skills and wild after-match parties. Their extremely reckless shenanigans during a match against the Appleby Arrows included allowing the Bludgers to go free and an illegal hunt for a Hebridean Black dragon to serve as their team mascot (the hunt was stopped by Ministry of Magic personnel). This incident led to the disbanding of the team in 1814 (QA5).
In everyday British usage, a banger can be a sausage, an old car or a firework (Oxford English Dictionary). Other definitions are a forceful aggressive athlete (Merriam-Webster) or slang for a wild party or a gangster/thug (Urban Dictionary).
Banchory is a town in Aberdeenshire, Scotland. Its Wikipedia entry lists several football teams, a basketball team (the Banchory Stags) and a rugby team (Deeside RFC), but no Quidditch team (Wikipedia).
From the Web
WizardingWorld.com (Pottermore) features:
- The British and Irish Quidditch League
- British and Irish Quidditch teams to support
- Things you might not know about Quidditch
- Quidditch Through the Ages
Harry Potter Wiki: Banchory Bangers