I'm in the UK too, most of us are.
I'm sorry you think your decisions were poor, they may have been the right decisions for that time. I've made plenty of decisions that I wouldn't make now, but which were the right ones at that time. It never is too late. I went straight from GCSE's to A Levels, then straight to Uni to train as a teacher. I had to give that up due to the health of my husband and myself. I have, however gone back to uni and am doing my masters degree.
When I was training to teach I had friends there on the same course and year I was who were in their late 40s. Really, it never is too late.
What is it that you wish you were doing?