Then you make it an election subject: will we follow
  the referendum or not?!

If we had AV or STV this might work - you could have "Conservative, exit", "Conservative, remain", "Labour, exit" and "Labour, remain" so the exit/remain decision was decoupled from the labour/conservative decision. But we don't, we still have the shitty FPTP election system.

I'm sure there's been some buyer's remorse among leave voters - but if remain can't win a remain-vs-leave vote, I doubt they'd fare better with a remain-labour-corbyn-vs-leave-conservative-boris vote.