> no room for negotiation in it. The government page itself spells out the hardline consequences

There is always room for negotiation. Bilaterals is a treaty, not a diktat. And again, 2 years provides time for another referendum.

> wonder how many Swiss were aware they were voting to end their own freedom of movement, that blocking EU immigration would mean they would no longer be able to move elsewhere in the EU themselves

Everyone did. The question was how the Guillotine clauses would be executed. Which, truly, nobody knows.