A lot of things were led by the UK in relation to Europe. Yes your right it predates the EU. I concede that. But your missing the point (as always).It does not change the fact that the Britons want to leave.
There would be implications depending on the laws passed by Brexit. You don't know what those implications are.
Its not a nonsense complaint at all. Thats the type of attitude that led to people voting to leave in the first place. Its a first step.
Legitimate concerns were not being listened to. Your understanding of or lack of how criminal enterprises use this to frustrate UK confiscation orders pretty much sums it up.