> It remains the case that the 4 most competitive financial centres in Europe aren't in the EU (Global Financial Centres Index). That's likely to continue once London and Zurich form closer ties.

It's not invalidating your point but assuming Wikipedia accurately reflects the index (https://en.wikipedia.org/wiki/Global_Financial_Centres_Index) the four most competitive financial centers in Europe are London, Zurich, Luxemburg, and Edinburgh.

Luxemburg is very much a member of the EU.