> Perhaps then should be a referendum to ask the "Euro mainlanders" if they want a UK with the privileges they have.

The EU mainlander area's elected representatives forged this deal.

The privileges the UK sought like the 'red card' system apply to the whole of the EU.

There's nothing stopping an EU country from getting the same terms on the integration bit, indeed some countries have done that to varying degrees - Switzerland (EEC), Iceland (EEC), Denmark (own currency), Norway (EEC with EU laws) & Sweden (own currency) & Turkey (customs union)

If you're a Spaniard don't you have to worry about Catalonia?

The EU allows states to 'minitiarize' and devolve down once the trivialities of sovereignty and the '3 basics' EEC principles are sorted out

  > Perhaps then should be a referendum to ask the "Euro 
  > mainlanders" if they want a UK with the privileges 
  > they have

The exact same sentiment (and it's an ugly one, I might add) was floated by less savoury corners of political discourse in England in the run-up to the Scottish independence referendum. It's not helpful; please don't stoop to it.

> Yes, but with the same rules than all the other countries

Plenty (if not all) EU countries have negotiated exception to various treaties. It's the nature of these "exceptions" which matter (like the UK wanting a voice in the Euro policy, despite not being part of the Eurozone, and doing everything they can to prevent reforms of their bloated and dangerous banking sector).