If you have no idea then that's your problem, not mine. And you're being facetious now.
I'm fairly certain I'm speaking in clear English; if billions of people want to fit onto the UK island, let them. If you don't like this, don't stick around for it.
If loads of squatters turned up in your house you'd just let them stay and instead move out because you didn't like it? I'm not quite sure I understand your logic or reasoning here.
How am I being facetious? You're saying your country would collapse if border controls ended from people flooding in, as if the whole nation was made of gold. Yes, I realize it's the place you live, but I don't have that kind of attachment to it, and nor will the other several billion people who have no interest in living there.
I have a house, and these people have none. I'm more concerned with understanding why there are squatters on my land, and why they do not have their own homes, than worried about getting them off of it; if they willingly became squatters and were just passing by, then so be it; I'd be a little more concerned with enjoying my life. Anyway, I wouldn't shoot them, or ask the state to shoot them, whatever your flavor is; perhaps not many will agree, but I'm concerned about society and actually interested in solving its problems. But ultimately the squatters probably aren't armed so a warning shot will get them off, if you really need them off.
However, this is a straw man. People living far, far away from me on the other side of the nation, that I'll never meet in person, coming in, and for me to have the nerve to tell them to get out; that's much different than having squatters on the land I actually own, as that is my business; the business of people I've never met, I tend to keep my nose out of.