// I rather thought that I was a free citizen. And that MPs sat in Parliament at my gift. And that European sots ought have no jurisdiction over me. //
It's not about jurisdiction. Any future of the UK in or out of the EU still will be based on a mutual relationship with the EU, so, by definition, you will need to reach an agreement with them. More to the point, the EU doesn't negotiate with Parliament, but with the executive. As is perfectly proper, of course. Just as in our proposed future trade deals we would negotiate with the leaders of other countries, not their legislatures.
So you need the agreement of the EU on any future relationship. Then that agreement will need to be put to Parliament for ratification -- if nothing else because this is now mandated in law, per the EU (Withdraw) Act 2018. Yes, MPs sit on behalf of the people, but it is they who pass laws, not us.
So you need the agreement of the EU, and then of Parliament. And finally, Parliament will either directly or indirectly be accountable to the people for the agreement they support: directly in an election, or indirectly in a ratifying referendum.
This is the practical but more to the point the only way through the mess. It doesn't undermine your status as a free citizen. It's literally how democracies work, and always have worked.
I'm blessed if I know what physics has to do with any of this. Would that politics were as easy as that. And physics is impossible.