The last official marriage bars in the UK were I 1973, but the fact they had been in existence meant there was still an expectation that many women would stop working when they married, and if not then, when they got married.
When we were clearing my father's stuff after hus desk, there was an unfilled tax return form from 1973, which had a section for dependent adult daughters. The '70s was also when you could start getting credit cards and mortgages without needing a MSN to sign off on it. And equal pay came in by law, and that's still not a reality everywhere.
It depends who you're looking at for care - some people always had nannies or au pairs, but that wasn't an option for most. In rural areas, the school bus could mean some children would have to leave early/get back late, depending where they were on the route (I was last on/first off for our bus, but for others their journey could be over an hour.) School finished later, too - our last lesson finished around 4pm, whereas these days, they all seem to be out by 3:15.
If Mum wouldn't be at home, she would often arrange for us to have tea in town with one of our friends, and then would collect us later - this was a massive treat for us, but was probably more about practicalities. And we sometimes had people come to tea with us, too. When we were primary age, Mum was part of a baby-sitting circle, so they could use that. There was one family we were particularly close to, and the four of us children were often all together at one house or the other. (This always had to be arranged, because we lived out of town, so we couldn't just walk there.)
I think there was a lot of support going in which we weren't aware of - a few months ago, I caught up with friends of my parents and she was talking about how helpful my mum had been to her at one point when they had housing problems and trying to sort all that with the children at school and work as well - I had no memory of it, and I don't know if it was because I just didn't remember or because I didn't know at the time. So I think there was a lot of informal stuff with friends and neighbours.