Ok, so OP can afford childcare when she goes back. She is 38 so hasn’t got time to faff around if she wants a biological baby. If she changed jobs now she would reset the clock in terms of being able to claim maternity pay. She hates her job so would rather take time off from this one than the next job. It would look better on her cv if she didn’t ditch the job now.
I totally see all those practical issues op. Many women raise a baby alone. It can be done. I see the job aspect of this and I don’t think you are being unreasonable. I have some suggestions:
1-Can I suggest you look into childcare prices in your area and total up the real cost, especially if you go back full time.
2- consider family support...do you have any? Do you have people to help you at your lowest points? Good friends?
3- How will you feel going back into the job? Some posters have pointed out that they hated leaving their baby to go back. I can tell you that I was bloody ready to go back to work. I always knew I would want to go back. What kind of person do you think you will be?
4- you don’t say what work you do but what is the job market like? Can you move quite easily? Will Brexit affect your industry?
5- are there any changes you can make in your current work place to make your job more bearable? Whether or not you have a baby? Change in department? Improvements to role? A manager you can speak with? Try to make life easier.
6- what route are you going down for this? How will you have a child? If you are thinking of being a single adopter then they will be interested in my points above and that you have thoroughly planned for it. Although if you are adopting you don’t need to rush due to biology!
It isn’t a daft plan if you think it through properly.