The core of the question is though, if now the majority votes for not leaving how can you deny their choice?
Wouldnt that be non democratic?
The majority can still vote no and cement the results of the first vote

True, but what is the point of having a vote if it is just ignored? Also what is stopping them from just voting over and over again until they get the result they want? No. This is all contrived establishment creep and PR trying to pull Britain into the EU against popular will.