Hi there w3bbo, you are right in saying that the Qur'an can be taken out of context too easily, this is indeed very true. You see, the Qur'an is comprised of the Classical Arabic language (deep and rich in vocabulary) which means that in order to understand it, one must study it for a number of years. It is a fact recognized by the linguists of today that the Arabic language has the best ability to express wide and deep thoughts and to explain important subjects in short and precise words. Unfortunately, as I'm sure you can understand - people make the grave mistake of trying to understand the Qur'an from the get-go.
With regards to the Muslim communities having to take responsibility to ensure such atrocities do not occur. I'm not sure they are obliged to take responsibility as such. There have been many Muslim communities denouncing the events of today, with many stating that the perpetrators were not even part of their communities. Additionally, many Imams and Mosques have spoken loudly against the actions of the Woolwich murderers, need they do any more?
As for those who partake in spitting at soldiers returning from tours of duty, burning poppies and the British flag on remembrance day. What can I tell you w3bbo? The vast majority of UK Muslims oppose suchay actions AFAIK and want nothing to do with such characters. I think the group you are referring to are Anjem Choudary's group (which no one really likes anyway).
Ultimately, you are correct in the sense that the UK Muslims need a louder voice. When such atrocities occur, people need to know that the Muslims are against such incidents and that their religion does not teach nor allow such unfathomable events.
I sincerely hope you understand.