This is all I can see that you’ve shared - but I may have missed something, please let me know if I did - so you bought a house at 21 with your DP and:
”we invested heavily in company shares (no risk), lived frugally but not in a joyless way. Always two holidays a year. Overpaid mortgage until mortgage free. Kids grown by now so could have 4/5 years of really aggressive saving. Both took voluntary redundancy.”
So how much do you think one would need to have invested to live off the interest? What sort of annual income do you find livable? I am happy to live frugally, been doing it my whole life!
Because even if we somehow managed to pay off our mortgage and then save up say £600k, at 5% we’d only receive £30k per year, which minus taxes etc would be tough to live on.