The Daily Mail reports that Britain is the most violent EU country here: http://www.dailymail.co.uk/news/article-1196941/The-violent-country-Europe-Britain-worse-South-Africa-U-S.html. However, the numbers seem high compared to this Wikipedia graph (http://en.wikipedia.org/wiki/File:Violent-crime-rates-UK-1981-to-2007.png, from the Violent Crime article.).
The Wikipedia article Crime in the United States reports U.S. murder rate is well above that in U.K. and other EU countries (see Homocide). The article List of countries by intentional homicide rate shown rates for all countries. U.S. is high for developed nations.
Finally, not U.K either, but the Empires of Steel article Video Games and Real-World Violence has some interesting graphs for the U.S. I believe they were all taken from the U.S. Dept of Justice.
This post is mainly intended to collect data w/o much comment. Briefly UK trend seems very similar to US. Method of counting is different. If Daily Mail stats are correct, something very strange has happened recently. Wonder if the data is the same (same categories, same source, same counting methods) and what their source is.