"They didn't 'leave it up to their MP to represent them', because it was a national referendum.
By choosing not to vote, they consented to go along with the majority outcome.
It would be sensible, therefore, to presume that:
65.2% are in favour of Leave
34.7% are in favour of Remain"
That's a bit of a leap of faith is it not.
It could quite easily be put the other way, the 27% thought that along with all the other reports that remain would win so didn't bother coming out to vote.
Parliament needs to represent everyone, put it to parliament.