The more general question here is that if the populace has indeed changed it's mind/mood regarding something on which some sort of referendum or voting has already taken place, should or shouldn't a second referendum/voting take place? There's an important catch here that we cannot know or be sure before a second referendum/vote actually takes place that the populace had/has indeed changed its choice. And since one doesn't and cannot know for sure before going in all the way towards a second polling, what rationale does one have to ask for a second poll in the first place?
A solution to this problem can be in the amount of "calls" that are being made - in newspapers, on TV shows, on social media, etc. - for a second vote. Of course, no strict mathematical definition exists and no easy definition can be constructed regarding what amount/quality/quantity of "calls" should be considered sufficient to invoke a second vote, but a "good" number of "prominent" people calling for a second vote and a "high" number of citizens expressing for a "prolonged" period that they've changed their choice should be good-enough a reason to call for a second vote. Using this admittedly vague, subjective, and unscientific threshold, it seems like a second Brexit vote should be held in the UK.
There's another factor to be considered, and the Brexit example is suitable to explain it. Like it's possible that a guy initially gets attracted to a beautiful girl but after living with her for a year realizes that she isn't worth it [and that his initial judgment about her was incorrect], it's possible that the attraction of Brexit was only initial and that the very detailed discussions, etc., over the past several months have made many pro-Brexit folks realize that it's in fact better for Britain to continue to be an integral part of Europe [and EU]. At least for major issues such as Brexit, a provision for "change of heart" should be kept, especially after detailed discussions have been held and the voters have had sufficient time to understand the effects of their majority choice in detail, so that they can now walk back from that initial choice if they want to.
