"So to assume you can have another referendum on the basis that you 'didn't know what you were voting for ...' the first time, is arrogance of the very highest order..."
Up to a point, I'd agree. But... wasn't this part of the argument for holding this referendum in the first place? That the people in the 1975 referendum didn't know that they were, ultimately, voting for a political union rather than an economic one? I've seen this argued several times on AB and elsewhere.
The main difference is one of timing. Owen Smith appears to be calling for a second referendum within a year or two of the first one. Even if you wanted the British electorate to "think again", that is way too soon by any stretch. But presumably no one would object to revisiting the subject, and holding a referendum on "Breverse" in 30 years or so, if the circumstances of Brexit were judged after the fact to be undesirable after all.
Also, yes, I was being a little facetious with that comparison. Still, as I say, we could be heading for a clash between our two forms of democracy anyway, depending on the timing and outcome of the next General Election.