@Magda72 I understand what you’re saying about when having children, families often decide it’s easier if the mother SAH or go part time... but that hasn’t happened here has it.
Let’s be blunt, OP’s children are still pre-school age and her ex’s twins are at least 1 which means he must have left her at least 18 months - 2 years ago. Doing the maths, if OP worked pre-children then she hasn’t (or shouldn’t have by the time he left) had a long period of being out of work so she isn’t as disadvantaged as someone who has given up years of potential career progression.
I’m sorry OP a lot of my sympathy was lost for yog when you stated that you wouldn’t be “much better off” by working. So you acknowledge it is a choice of yours not to work because you would be better off, but just not enough for you to think it’s worth disrupting your life.
Any extra income would be great for your family, even if you were £20 a week better off that’s £80 a month!
Not only that but you’re disadvantaging yourself through choice. The longer you’re out of work, the harder it will be to get back to work. Your kids will go to school and then what? You’ll just continue to stay at home and not attempt to support yourself?
I’m sorry but I’m inclined to agree that you and your ex have both chosen to be feckless and not work.
Also, UC and a part time job at NMW would be more than enough to cover childcare costs. I know, I’ve done it. I was a single parent for many years, also with no CMS to support me.
Neither parent is working to support the children. Both through choice. You’re as bad as each other.
I agree with others though, I wouldn’t be facilitating contact by paying to drive the kids to his home. If he moved, he can make the effort to see his children.