Remain and remain.
As others have said, the 2016 referendum was advisory. It therefore had no minimum threshold or process for voiding the result in case of unlawful campaign/voting activity.
It was a very narrow win for Leave, nothing like the 2/3 supermajority that most mature democracies require for such a massive change to their constitution.
The Electoral Commission has found that there was unlawful campaign activity - the Leave campaign funnelled 10% of their approved spend via another campaign group. They broke the law. However, because the referendum was advisory, it cannot be voided. It is a loophole. Watch this link www.google.co.uk/amp/s/amp.lbc.co.uk/radio/presenters/james-obrien/brexit-referendum-corruptly-won-but-result-stands/
I do not respect the 2016 referendum result at all - it was advisory only, plagued with unlawful campaign activity and just full of lies and vague notions of having your cake and eating, on top of the big red NHS bus lie.
Even if the 2016 had been binding and fought in a clean and lawful way, I still don’t think that having a referendum now, based on better informed choice of the WA and PD versus Remain would be undemocratic. It is a different question. 2016 was vague, 2019 would be detailed.
I additionally reject any notion that the 2016 referendum has been ignored. Unless I’ve dreamt the last 2.5 years, the government has invoked Article 50 and spent nearly 2 years negotiating the WA with the EU27. That would not have happened if the result had been the other way round.
Oh and as David Allen Green says, 'A mandate can be either democratic or irreversible. But it cannot be both.'