Homosexuality remains a source of contention for many religions who view it as an immoral practice. This does not change based on where someone lives: there is a population of British Muslims who do not tolerate homosexuality, and there is a population of American Muslims who feel the same way.
No, British Muslims are not more tolerant of homosexuality than American Muslims. A news story put out this week states that %52 of British Muslims are against homosexuality. American Muslims are not as well organized as British Muslims and tend to go along with American cultural norms more than British Muslims are forced to do.
Violent attacks on gay bars in America have long been common. In fact, in 2015, a Pew poll found that American Muslims were more accepting of homosexuality than evangelical Christians, Mormons, and Jehovah's Witnesses. British and American Muslims have both faced the same problems with integration into Western society, so it would make sense that there were equally tolerant or intolerant of homosexuality.
Many Muslims living in Great Britain have not assimilated into British society like their counterparts in the United States. America has always been seen as a melting pot - a place where different nationalities and cultures can come together to become Americans. Unfortunately, many Muslims living in Europe have not had the same success when it comes to living in European countries. In short, because Muslim Americans are more likely to assimilate into American society, it is likely that they are more tolerant of homosexuality.