Firstly, I would say that the UK tends to be more classist than racist. There is a palpable disdain from the gentry for people who are perceived to be leeches on society; ie people on benefits or government assistance.There is also an existing dislike for people who come from mainland Europe (mainly Poland) that take their jobs....and are on government assistance. So there is certainly an undercurrent of classism in the UK, and ethnic minorities just so happen to fall into the class that has a preponderance of individuals on government benefits.
That said, I feel a reason the intensity of the racial discontent in the UK is not as much of a talking point as it is in the US is that not only are black people a smaller minority in the UK, but they lack the economic and political power that US blacks have. If you are a black in the UK, the most fundamental route towards economic empowerment is to become an athlete. These are the people the young, urban minorities are looking up to - the football players. Sure there are immigrants and children of immigrants who have seen some success individually in the corporate environment, but by and large, there isn't the progressive collectivism (albeit to a small degree) that exists with blacks in the US (think HBCU's and the like). Mind you, blacks in the US themselves have a long way to go towards economic empowerment. On the political side of things, I do not believe blacks in the UK have a real voice. Even in London where they have a presence population-wise, they are still outnumbered by the ethnic British population. They don't have a constituency where they can have some sort of influence on national politics. In the States, at least there are numerous black mayors and Reps. I would really like to see a tally of the black people in the UK Parliament. People like Diane Abbott are few and far between.
That leads me to my point. Without even a semblance of unified economic or political power, you cannot be perceived as a threat. Blacks in the UK can live in a relatively safe environment, unmolested by society because they are not seen as a threat. Blacks in the UK are yet to have a real civil rights movement that will shake the very foundation of the London Bridge. There isn't overt racism from the system simply because the system does not fear you as it were. Once you become a threat to the system and their existing way of life, then you will see the backlash as it occurs in the US. Blacks in the US are a perceptible threat. They threaten by numbers, influence on culture, increasing economic power and education and the like. Moreover, they do not take oppression lying down - at least they did. The formation and subsequent destruction of the Black Panther Party is an attestation of the fear that blacks in America can put into the system. Well until you black folks in the UK can wake up and realize that all that glitters is not necessarily gold, then you will continue to be content with your status quo.