We've done this several times. More or less every voter votes for what benefits themselves and their family. The grey vote have been bought by the Tories since always.
Again though you are suggesting people voted on one aspect of the labour manifesto when it's unlikely that was the case.
I would think many of the younger voters came out this time due to tuition fee bribery rather than brexit. As for the older voter they were more likely turned away from the Tories this time due to the assault on winter fuel payments and the dementia tax.