Much of what Stephen Fry says here is correct. London already has a global tax haven status if you are outside British dominions this will gain strength after Brexit and will only increase the UK wealth gap. Funds will be domiciled here on a low if any tax basis, financial bonuses will be paid on a low if any tax basis.
Trump’s tax deal has increased corporate profit margins but not perculated down to wage increases. Somerset Capital Jacob Rees-Mogg’s company has relocated to Dublin this could change with no deal Brexit and cheap fund management domicile in the UK. Luxembourg, Liechtenstein, Channel Islands, Isle of Man and to a degree British dominions Bermuda and Cayman Islands have already been pressurised out of the offshore business mainly by EU legislation.
Immigration has always been a Red Herring. This is a game of deregulation a game the EU has been combating.
This direction will increase a governments concentration on London the North of the UK will continue to suffer from low investment especially with reductions in industry such as cars. You have already seen where British steel is going. Farage, Johnson and Gove are extremely dangerous and financially motivated much of this is about securing for the rich the London driven financial services industry a necessary industry but not at the expense of the country.
The US has been securing the control of the global banking system for sometime now. The big blocks China and the EU to a lesser degree Russia will be able stand up to any US pressure. Britain will be exposed both financially and trade.