when will the prime minister stop mass immigration

I think you mean illegal migrants rather than just migrants. Well, we have to house them in proper conditions per the human rights convention. However it shouldnt be cushy and we defintely need to expedite those that dont qualify.
On the flip side, manyare putting their and their kids lives at risk just to get to the UK. So how bad is their country. We need to be sensible about this.
They want to live, we need fruit pickers etc. I say make it a win situation. Put them to work to earn the money to live while we process. That way it helps everyone including tax payers.
Doubt that government will do that

I would try and ascertain whether the argument you're trying to make is about those foreigners who chose the right way to come into the country and declared their request for asylum.
Or whether they chose an illegal route and are here illegally.

The bigger issue is those illegals who enter the country and then have children here.
Because by international law that makes the children British by birth and thus British subjects and the parents subject to deporting.

At least Latin American have roots with the west. The other Nations don't and have foreign Gods so I seriously doubt they will mold.