if the polls do what the polls in the US did and underestimated wwc vote, could that be good for labor?
WWC turnout is already accounted for with a 75% turnout (on a 1-10 likelyhood to vote scale).
It won't go much higher than that ...
If Labour does surprise today, it will be more because of a comprehensive shift towards them from all population groups - as a form of protest vote against recent security flaws (May is the incumbent PM and has "failed" to protect the British public from these attacks). Even though the attacks can certainly not be blamed on her personally, the public might still "punish" her in some way even if they don't agree with Labour - not even to mention Corbyn ...
Still, the odds for this are low.