Honestly in your position I’d investigate if both your employers would be open to you dropping to 3/3.5 days a week for a year or two while both kids are in nursery.
Every day you drop would surely save you in the region of £800 a month in childcare.
With similar salaries you’d not save much but it would be a couple of years of slightly more relaxed family life, which might be nice.
If one of you earns a lot more than the other then the lower earner dropping to 40-60% work hours for a couple of years would save you a lot. I’d always say it’s not the best idea to give up work altogether but part time (if you can get it) can be a really good compromise.
Alternatively you just keep going and know you’ll earn more later/have less expenses later and while it’s a bit soul destroying now it gets better.
It does highlight the issues of housing/building costs though as it’s that driving both your house & childcare expenses to be so high.
We are in the north east and our gross family income is significantly less than yours but take home is around £6k, mortgage is half yours, childcare is slightly over half for local 7:30-6pm outstanding nursery, day to day living costs are generally lower, commuting is pennies (mainly wfh/bike).
Kids are not at nursery anymore but even if we had fees to pay we’d have around £2k a month after mortgage, bills, childcare & commuting. I often think it must be so hard for friends in the south as even on better salaries than us (& ours are decent) they always seem to have much less disposable income and they also live in much smaller/less pleasantly located houses. Property costs are a real issue.