Britain has a large welfare state, most of the border, welfare and council offices are staffed by foreigners, so they know they will be able to reap a lot of benefits. It is not just the direct benefits, it is all the indirect benefits. If they go over and have a child, they are literally set for life. They get a free house, free education, monthly pay check and free health care when they need it.
The other reason is that Britain has the strongest currency in the world and a very productive economy, compared to other countries, for people who want to work or have a skill to sell, they see it as a means to send a lot of money back to their families and live a high standard of living.
They will never be able to change this welfare state now, there are too many people benefiting from it.
I read an article about how NHS tourism (foreigners coming to the uk to get free nhs treatments) actually benefits the economy. This guy went out of his way to make out as if these people coming to the country helps because they spend money on other things while they are here. This is just bad economics and no wonder we are in £1 trillion debt with that attitude.
I have been saying for years in welfare related threads that most of the immigrants that come to the uk, come for the welfare benefits and not the job opportunities. The job opportunities is of course a big factor, as i explained above, but the primary reason to come to the uk is all the free stuff the government hands out.
There are even people that think we could have complete open borders with our current socialist system and it wouldn't cause any problems.
Asylum is a joke as well. The whole asylum thing should be completely stopped. In this day and age there is no reason any one should realy be claiming asylum. They can travel any where in the world if they want and most countries will let people in. Often the countries they are coming from are not even that bad. It was meant to help people ravaged by war but now its letting people in for no good reason. Why don't they go some where else and claim asylum? funny that uk gets all the asylum seekers? I would completely end asylum if i had the power.