Buy a complete new belt from Vauxhall, and get them to fit it unless you know exactly what you are doing.
DO NOT ATTEMPT TO REPAIR IT
DO NOT FIT A 2ND HAND ONE
The reason is simple.
It's the only thing that keeps you in the car, rather than going through your windscreen in the event of an accident.
It may cost you more but you don't know what has happened to a 2nd hand one, and I would never repair something that is safety critical.
Please don't take chances with your own safety.
Traffic lights in London are just rough guidelines