I do not have a degree, or A levels.
I started work as a London temp in admin, travelling into the city daily. I progressed naturally into a permanent role then took on the tasks no-one else wanted to do.
I moved around a little, once due to lack of flexibility post maternity - I thought that was game over.
I did the tasks I was given and became an expert in a niche area that no-one else wanted to own. As my management changed over the years, I was leaned on more for my knowledge.
My biggest boost came when HR accidently sent me my male colleagues compensation details & it became apparent I was earning far less than them despite being the same job grade, resulting in a 60% pay increase.
I'm now on ~£125k base + 20% bonus. Not the ball park your looking for, but I've got here without parental support, friends in high places or a high level of education.
I took 2 rounds of maternity leave (negotiating 80% wfh after the 2nd) & my husband made a career change ~5 years ago to a lower paid, higher satisfaction job.
Believe in yourself.