I wonder how many of the critics here, at least those living convenient to cross-channel services, have made trips to France to buy booze and/or fags. It's the same thing. If it becomes possible to make international choices then tax rates become a competitive market.
If a country decides to go the high tax route to gather as much tax as possible from those who aren't mobile there's absolutely no justification sitting and howling* about injustice if tax-payers, individual or corporate go to Hong Kong, Ireland or anywhere else. The decision should have considered these factors.
By adopting more generous rules to high net worth individuals the government has, over the years, gained more tax than it would have done if those individuals hadn't chosen to be here. There are only two questions here:
Does the presence of those individuals with their spending power distort the local economy to the detriment of the rest of us, e.g. in the housing market?
Will these changes lose more from those who move away than it gains by increasing taxes on those who stay?
*Except, of course, the justification of political theatre; shift the blame from the politicians who made the decision in the first place.