I agree that the EU will quickly get over the UK's departure and far from disintegrating, it will move forward happy to be free of our idiot representatives in Brussels.
We already know that they have the banking matters in hand and London will lose large parts of the business it does currently to various centres within the other EU countries. Ultimately, I would expect some centralisation and one can guess at the venues in any short list.
Clearly, it would not be in the forward interests of the EU-1 to allow the UK to quit yet still retain any of the 'nice little earners' as that could upset several of the main players. It stands to reason therefore, that the UK will fairly quickly lose those trades with and on behalf of the 27 remaining EU states. Our entitlement under 'passporting' arrangements has been a lucrative part of our EU membership, I believe, so it's not difficult to see that 'the ball is in the EU court' and there isn't very much the UK can do about that.....but we will have 'taken our country back'!
Tom