Yes, bangers are sausages. That is the first thing an English person would think when they see this thread title.
Also it's a crappy old car like students used to have when I was a student (late 80s / early 90s). One where you might need to kick it or hit the starter motor with a hammer before it would start. Or maybe you'd have to push it. And randomly things would not work and then they'd work again for no reason. And you'd just hope everything worked when you took the car for its annual MOT test. That is a banger.
These days in England students seem to have nice new looking cars because they have huge loans and massive debts, but 18 years ago we used to buy a car for £200 with bad paint, scratches and dents on it and we had to go down to the scrap yard (so called "breakers" but they never seemed to break down the car in those days) regularly and lie under a car in dog poo trying to get parts off another similar banger.