I'm sure there are ways around childcare costs such as having the baby in nursery only 2 days a week, 2 days with me, 2 days with dad.
My partner is open to find a place near London if we can find a gem: countryside-ish house super well connected to London for us car-free people.
How long did you actually live in London OP? Was it brief? You sound a bit unrealistic in your expectations. If you're looking at the price of 1/2 bedroom flats in zone 3) I think you are going to struggle to find an affordable house (and certainly not a 'gem') which is suitable for non-drivers.
You sound like you are not very clued up on the transport situation either. Without any family support you are going to struggle with the delays as you will probably need a back up for collection several times a week possibly for a few hours each time.
I don't think you would find it easy to find two jobs where you and DH both could regularly take the same two week days off either. As I said earlier, most of my friends who have stayed in London are child free. And you should take into consideration the fact that if you come back to London you may well find that you cannot get yourself into a situation where having a family is affordable.
You don't sound like you are high earners. Realistically in that situation most people have to decide whether they are going to leave London and even the South East to have a family or stay in London and not pursue having a family.
Mumsnets readership does tend very much towards high earners. And when this question comes up you always get people saying how marvellous having children in London is. But often it really is not an accurate reflection of what life is like in London for people who are more ordinary. And while on paper people talking about commuting to Brighton or Ramsgate sounds okay, when you factor in train delays, childcare, work/life balance etc it's not great.
Also, saying Scandinavia is great for babies but not adults. It's probably good for adults with children though. I think you might have a bit of a naive view of parenthood too. Life does change. You're viewing life in London through the prism of your child free life. Life changes when you have kids. They have bedtimes and are fussy eaters and get bored easily. It's a nice idea that you will be eating out and taking in culture all the time when you have kids. In reality there will probably be an awful lot of boring evenings in, washing, ironing, cooking, making packed lunches, nagging, cleaning and tidying up. They are much the same in London and Scandinavia. The difference is, if you live in the South East often they take up your only free hour a day and most of the weekend. Somewhere with a better work/life balance would be much more likely to actually give you the opportunities to do the things you want.