I have read this entire thread, and I have to say, I empathise with the OP. We are in a fairly similar position - sky high nursery costs and a huge increase in our mortgage means we now break even every month or go slightly into the red, whereas we were able to save a couple of hundred each month before.
It’s disappointing to see the scathing responses you have received from posters on very low wages or universal credit. I think if you’re used to having most of your expenses heavily subsidised or topped up, it’s easy to lose touch with just how much everything costs when you pay the market rate for it, as well as high taxes which in turn pay for other people.
50k is bugger all with a mortgage and full childcare costs unless you live somewhere unusually cheap. For a start, your take home would be about 4,100 per month after tax. If you pay 1,500 childcare and 1,500 mortgage, that leaves about 1,000 for everything else - bills, food, car costs, one off expenses and repairs, clothes, child related expenses, birthdays… you might not be heavily in debt but it’s easy to see how money gets tight and breaking even every month becomes the norm.