I had to search back through the thread so I could quote your post.
Of the 7 criteria on your list, the only one I sort of meet is the degree, and even then it was just one of the sciences (not medicine) lol I was also born in the Home Counties, though my parents originally came from abroad.
For me and the people I know who earn salaries in this range, the world has changed a lot, and it’s far more achievable for ordinary people who worked hard when young to now be in a highly paid field than it was in the past.
In my circle all of our parents emigrated from Commonwealth countries (not Can, NZ or Aus lol) to the UK, all parents had jobs like nurses, bus conductors, taxi drivers etc. We all went to state schools, other than a couple who won scholarships to private schools.
The common thread we all have is the huge amount of importance our parents placed on education. Working hard enough to get into uni (only a couple Oxbridge/Russell Group), and getting into a decent career path with a solid trajectory following. In my case this was Chartered Accounting/finance purely because I always loved numbers (and still do!). I really enjoy my job as it makes a difference.
Moving jobs regularly also helps. I’ve told this story on MN before however my largest pay increase in moving jobs about 10 years ago was from £87k to £125k, up by 43% in one move for a very similar role in a larger company. The single thing I thank my lucky stars for was not telling my new employer what my old salary was during negotiations. These days if asked current salary, I pivot the question towards the new role being discussed and what I am looking for.
For anyone who doesn’t meet the 7 criteria, keep going and aim high, as in my experience it’s far from impossible (and not even that difficult, as long as you persist!).