Re: How?
And indeed Brexit wasn't an option without the express consent of the EU
Rubbish.
Article 50 spells out an agreed mechanism for leaving. Before this, states could still leave, there was just no established procedure as to how.
Our membership of the EU is established by an act of parliament (and agreed treaties). Parliament could have rescinded that act at any point, and abandoned the treaties. There may have been consequences, but parliament always had that option.