Speculation is all well and good but the final/if necessary option will be to walk away and let the good old 'net payers' pick up the tab.
After that, any and every punishment possible will be enacted upon the UK, mostly in the form of tariffs. The UK will reciprocate in kind, knowing she imports more than she exports so the sums will be balanced in her favour.
The outcome....both sides of the Channel bleed one another and hopefully will eventually come to their senses.
But hey!!....this is politics right?
Could be a totally different outcome then
I know I've posted this before but there is a ring of truth in it as well as a widespread growing of support in the UK for its content.
Perhaps I'm a little too patriotic but having worn the Queens uniform I take a great sense of pride in much of what my country has achieved on the world stage over the last century in particular.