The loss of the UK wil make an immediate dent of about 5% of the current EU budget (the UK's current contribution - less what it takes out). This has already led to more downbeat forecasts of GDP growth in the Eurozone.

Additionally, if exiting the UK causes a drop in its growth, as is predicted, due to uncertainty over the strength of th pound amongst other factors, it will also result in a drop in imported trade from EU countries. Add to that the possbility of exort tariffs and that cold again shrink GD growth in the remaining EU states by perhaps 0.25%.

Britain has generally attracted by far the highst amount of outside investment in the EU. Once removed, it is possible that this investment may remain in the UK but many large investors have already spoken of their desire to maintain access to the free movement of goods in the EU and their willingness to relocate to secure this. Emmanul Macron in France has spoken openly of a desire to steal financial services away from the city of London, quite a coup for France if that could be achieved and quite a blow to the U, which has long relied heavily on the CIty of London to provide a chunk of GDP growth.

In terms of individual EU countries, Ireland may well suffer the most, dependent as it is on trade with the UK, particularly benefited from an open border with Northern Ireland.

Belgium, the Netherlands and Luxembourg all have a strong interest in the UK as does Sweden. The Flanders region may lose 2.5% of its GDP to the changed trade relationship with the UK.

It's harder to judge more fluid effects like the raising of tariffs reducing the openness to trading within Europe. There will almost certainly be such difficult ot anticipate effects, perhaps even effects invisible in the short term and be argued about in the years ahead.