Indeed. Unfortunately in the age of abundant air travel and being able to do basically everything online, including remaining in contact with people, it's not hard to just move out of the UK if you're super wealthy.
We absolutely can and should tax assets that can't be moved out of the UK, though, like land. A multi-millionaire can move all kinds of things out of the country, but they cannot take their land with them. Land value would of course go down or stagnate, but I don't personally see that as a bad thing.
That said, even if you took all billionaire wealth in the UK (while somehow simultaneously preventing a crash in the value of those assets), it'd last months. It wouldn't be a permanent solution. State spending is £1.2 trillion, a small amount of billionaires aren't going to plug the gap for long.
There's no simple solution to the financial situation this country is in.
E: I guess people don't want solutions, they just want someone who agrees with them.
There are a number of sources for it. I'd have thought you've seen them since you're posting this nonsense
But sure, here is one.
Why are you fine with holocaust denial and genocide? Do you also deny the Holocaust?
What a disgusting little bigot. I hate racists.