But why would they flee from a country they feel has too few rules about controlling knives (and thus a feeling of lack of being safe) to a country that has few rules about any weapons. Not that this is an insult as I respect (even if I don't always agree) that this is the way US citizens want to live. Fine, their country not an issue (except when they want to say that my country is not free and we have to adopt US gun rules because that is the only way a country can be free, then the fun is over and I will vehemently disagree with having free gun laws in the Netherlands
).
But I think if they have qualms about knife crime/lack of weapon control/violence, they would be much more likely to emigrate to a country like Australia, Ireland or New Zealand. Or simply move to mainland Europe were there is no current epidemic of youths running amok with machete's and zombie knives.
If for no other reason that most countries in Europe have about the same system of providing affordable healthcare. And I think Australia, Ireland and New Zealand have similar affordable healthcare options. When coming from and NHS system to no system would be a shock to a lot of English people's system.
The real problem in the UK and for example in the US and some other first world/second world countries are gangs. Gangs are really the root of all evil under youth violence in the UK. Gangs are armed, they are omnipresent and it makes even those not in gangs have to feel they need to have a knife on them to feel safe. In the US it is the same thing but then with guns rather than knives.
Gangs are a source of great problems in any country that has them. Not only because it increases feelings of not being safe in your own neighborhood (crime, loitering, littering, nuisance) but the main thing is that it leads to turf wars and youths not involved in a gang to feel unsafe without a weapon or in the worst scenario they join a gang to feel safer as there is safety in numbers. The same goes for a lot of biker gangs who are 1%/outlaw biker gangs. Turf wars and just like a lot of youth gangs they start dealing in more serious and more serious crimes. Drugs, prostitution, forced prostitution, gambling, robberies, shootings, and many many more crimes will become gang territory the older and the bigger the gangs become.
You cannot bring an end to knife violence in the UK without fighting the gangs at the same time. The big joy for the UK police is their CCTV system. It makes tracking these thugs through city centers much easier as is catching them committing crimes in areas that have CCTV. Because as they are criminals, a lot of them are stupid and still commit knife crimes/beatings/robberies/etc. etc. under the watchful eye of the CCTV operators.
The problem is IMO the relatively high poverty and lack of belonging under many ethnic teens in the UK. That is why so many problem teens from these groups are pulled towards gang life. They feel second class it seems and this gang life is giving them both money and status, things teens gravitate towards, in large cities especially minority kids. Minority kids who if they were living in a village would almost never go into gang but in the anonymity of large cities they get pulled into gangs and the violence that comes with those gangs.