The leavers are fully aware that the majority would almost certainly vote to stay if they were given an opportunity to re-confirm their decision

That is simply an opinion with zero data to support it. Conversely the surge in membership of the Brexit party would suggest perhaps the opposite is true.

Degree level education was only available to a minority in my day, so in this sense there will be a correlation with age. But don't look at that, look at O levels and GCSEs, which were/are available to all. Those with 5 or more O levels, or GCSEs grade A-C, are much more likely to have voted remain.

The same correlation with age occurs for OL and GCSE making your argument fallacious.
Percentage of School Leavers Achieving 5+ A-C (or Pass) O-level or A*-CGCSE (1962–2006)
15% 1962
24% 1986
58% 2006