from common market
Both sides in the UK have their ideologues, whether they be federalists or isolationists and the fact we voted to be part of the common market is totally irrelevant in my opinion. The ideologues against the EEC included Benn and Powell whilst the advocates included Heath and Jenkins. It is an issue that divided both main parties back then and still divides both parties today.
There is an argument that our failure to buy into the EU project and fully embrace it allowed the other constituent nations federalists to gain the upper hand, if we had of truly committed to the EU we could have halted that progression towards federalism if we had so wished, but I think you underestimate the feelings of the other nations who do consider Federalism to be a future goal. I don't think they have been insidious in pursuit of that goal, I have always assumed that is the natural progression from common market to federalist state and as I have stated I am in favour of a fully federated EU only if there is a fully accountable democratic system in place with an elected President, a system of regional parliaments and supranational political parties. Obviously voting remain/status quo was never intended to give that option to the people which is one of the failures of the referendum and the reason I could not vote for remain.
I also think that you choosing to use the word insidious creates the impression that the EU always meant the UK to be subjugated to its whims and be a secondary state rather than a powerful voice inside the EU. That impression has been skilfully manipulated by the isolationists into making people believe we are a subsidiary to the democratic process and that we are marginalised rather than central to its future, I believe that has made us look a small minded nation who are somewhat aloof to the perceived common good that the EU could achieve if it became a fully federalised state. That is the bedrock of English exceptionalism and that exceptionalism is damaging to our standing in the world. That we are prepared to accept that damage is quite mystifying to me because I always considered the UK to be a nation of vision not introspection.
Saying that what is done is done and we must accept the democratic process and leave and if we are to leave it should be without any sort of deal and then we have to search for a role in the world that suits our capabilities, I am not buying the sunny upland unicorn imagery of the isolationists as I believe that to be utter nonsense and the powers that be have been remiss in trying to sell that to a gullible public. We may prosper, we may not, but democracy must prevail.