The problem in Britain is huge because
a) they were a colonial power, who gave rights of entry to citizens former colonies, eg what is now Pakistan, and
b) at the same time became a socialist state where money has been used as the means to keep everyone “stable” if not “happy.”
This has created an almost unstoppable cauldron of “unhappy” dangerous people living all over the country.
They are at huge risk IMHO!
It is interesting that many who have remained in the former colonies and not come to Britain when they had the right to - many do not as we have now limited immigration from these countries - the people that have remained if not publicly but often privately point out they were better off when they were a British colony.
It is those who have left their country often because they were probably in some sort of criminal trouble there that are more vocal and anti British people.
Yes we have created the problem for ourselves but it was unfortunately done for the best of motives because governments felt that certain people might be in danger to remain if it was thought they have cooperated with the former colonial power.
b) at the same time became a socialist state where money has been used as the means to keep everyone stable if not happy.
This has created an almost unstoppable cauldron of unhappy dangerous people living all over the country.
The UK also acted as a sanctuary (or "political asylum") for Islamists who had been convicted in other countries (Middle Eastern and European) of terrorist activities. They ignored pleas from the French to extradite certain characters and it was the French who originally gave London the title of "Londonistan." Our own FBI wanted to get their hands on certain of these people, who were involved in planning terrorist activities in the US, but the UK wouldn't allow this.
The FBI had warned MI5 about one of the characters who later became one of the London subway bombers. (He was connected to a cell in Brooklyn.)
Before 7/7/2005, MI5 thought they had the situation under control - they would give these guys political asylum and government benefits, and leave them alone to do their plotting and incitement. And in return, there would be no violent activities committed in the UK. But al Qaeda got impatient and told the Islamists to get with it, as far as the UK was concerned. And on 7/7/2005, MI5 got its wakeup call.