It isn't only British people that are violent. All countries have their violent groups. But there does seem like a propensity for young British men to want to live out some sort of "East End gangster" fantasy, LARping as a Lock Stock and Two Smoking Barrels character, when they get drunk.
As someone said, Thailand is a place that attracts this kind of Brit, while you find "Bogans" more common in Bali.
The thing with the British is more an issue with alcohol. They're wound pretty tight, and there are certain demographic for whom "drinking, f*cking and fighting" form the basis of their masculinity and pastimes.
Brits are actually known as being very polite in most places around the world. There's just a few places that purposefully market themselves for the "Oi, Oi! Lads on tour!" types, who go out wearing football shirts with their names on and try to get as drunk as possible. (Eyebeefa, etc.)