I’ve seen a screenshot of the results of a ComRes post EU referendum poll, asking voters if they are happy with the results of the referendum result.
The polls shows that 1% of Leave voters are unhappy with the result. Given 17.4 million people voted Leave this is 174,000 unhappy Leave voters.
There was a winning margin of 1.3 million votes and even if all of the 174,000 Leave voters actually have buyer’s remorse and would have voted Remain, it would still have been a win for Leave, albeit with a reduced winning margin of 0.95 million votes.
For Remain to be able to claim buyer’s remorse is a significant factor they need to be able to show that at least 4% of Leave voters were unhappy.
For the sake of full disclosure: I voted Remain
Edited to add:
So I went onto the ComRes website and found a margin of error calculator. So I stuck in the figures of 33.5 million for the population size (total number who voted) and sample size of 1,069 (given on the screenshot) and got a margin of error of 3.0.
This means the buyer’s remorse effect is just on the edge of the margin of error. But only just.