After lots of conversations with the Brussels representatives of other EU governments, I have come to the conclusion that the "two referenda" scenario described above is wishful thinking. If the UK voters vote "No" in the referendum, the other EU governments will simply let the UK leave the EU and treat it as a non-member state. There will not be any post - referendum negotiations.

David Fuller's view

Thanks for the feedback.  You could be right but EU officials will not want to lose their second largest economy, which is a net contributor to the Eurozone budget.  Some changes in the UK’s terms of membership are inevitable, in my opinion, but we will see what is offered over the next year and-a-half.