I qualified as a solicitor in the 90s, and was in mid 30s when I had my first child. I had 7 years PQE by then, and it was manageable, in a national private client firm doing litigation. I was fairly senior by then, so could demand some flexibility, and had established a reputation.
If I had been very junior I think life would have been difficult.
What I understand from the junior end is that life is incredibly competitive. You will not get far if you are rushing out the door every night , at 6 or so, you may be better off in house.
There are so many people looking for training contracts that you will really need to be stellar academically and have good work experience to get a foot in the door even as a paralegal, which did not exist when I started work.
The paralegals who work at our panel firms, I am now in house, are on zero hour contracts.
If you want to get in to decent firm, you will need a 2.1 or above from a Russell group university, and be prepared to work long hours for at least the first few years.
Solicitors firms, large or small are all about how much money you are going to bring in, and the top tier firms are very very intellectually snobby.
If you want to do corporate, you are really going to need a good nanny.