A lot of things are unknown territory, so newspapers like to imagine all kinds of stories. They are lucky as it is very easy now to produce enough pages to fill their newspaper.
There will be probably pleasant and unpleasant things for both sides as nobody can estimate the real and total impact of a Brexit.
The only thing that is clear, as it happened already in past, is that if big companies leave a country for any reason, they will probably never go back. Once lost it is for "ever".
The reason why is purely economical: they move because the location became too expensive or working on a normal level became impossible (trade tariffs, changed legislation...). As a move is a very expensive thing, companies try to avoid it, or postpone it till the move becomes inevitable. But once the move is decided there is no way back. Once gone is gone forever. So it is very clear that the UK will probably lose a lot of business that will never come back, or at least their growth will be massively smaller in future. At the same time the growth within the EU will be bigger as big parts of financial London will move back within the EU where it logically belongs.
So London can never become a winner in the financial sector. Now already parts have been moved and new businesses will start within the EU as that is their core business market. The financial sector will not take the risk of opening EU business related in the UK as they are never sure that, even if the UK stays in the EU, the Brexit problem will not pop up again.
