The past:
I just watched a very sympathetic documentary about the life of Sir Winston Churchill. Even in his era, they were talking in the U.K. about a "United States of Europe" (U.S.E.) I think the European Union is what they got. It wasn't perfect but the main goal of no more world wars out of Europe was achieved. That and NATO are not small potatoes.

The present:
I think a multiple choice referendum is the best way out for the current UK:

1)BREXIT MAY - Accept the terms as promulgated by EU and Theresa May.
2)Cold BREXIT. Leave now and negotiate after.
3)Abandon BREXIT entirely (BREXIT EXIT) as thought the first referendum had gone the other way AND make it a 2/3 or 3/4 majority for any future single choice referendum to leave.(assuming the EU will have you).

Those are the clear seamless choices UK has because the EU has laid down the law. They've done you a favor and kept it simple.

Since this is multiple choice you have to determine if it will be a simple majority win situation or you want to have a minimum percentage of electorate on the winning selection. But that is simple enough for anyone to understand and gets the political 'leaders' out of the loop since they seem to be bogged down by the situation.