My understanding from Brussels is that there is no second phase of negotiations. They just voted for a hard Brexit.
There can even be no extension of Article 50 for more than a few weeks, because we're electing the European Parliament in May. If the UK is still in the EU by then they need to elect MEPs, as well.
But their seats have already been agreed to be distributed to smaller countries who were underrepresented so far.
It would be a complete clusterfuck, including doubts whether any legislative action would survive court, if the UK isn't properly represented (either because they don't care anymore and don't hold elections, or they simply cannot organize elections on such short notice).
For Remainers(Anti-Brexit) the agreement was to start the process to leave the EU so of course those people didn't like the agreement either.