This is really interesting as I have also been wondering how people manage with more than one to pay childcare for.
I have one DS aged nearly 3, am expecting DC2 in November. Am about to be made redundant. Have already calculated that it's not worth me looking for a job until DC2 is 9 months - and maybe not even then.
Until now I have been on the higher salary of me and DH (if I was f/t) but working 3 days p/w. All the jobs I have seen which I could apply for are lower salaries than what I've been on (because the better paid roles are f/t ones.) None of them would leave me with more than £260 per month after childcare and travel, when I could claim JSA which is £240 per month - I decided it was worth working for £80 per month but not £20.
Plus there is the difficulty of finding a job whilst pregnant if you are soon to be going on maternity leave.
I have decided to go on the dole for 6 months (apparently for first 6 months it's based on NI you've paid not means-tested - after that they look at your savings, partners earnings etc) until the baby arrives, then claim maternity allowance for 9 months.
But when that finishes, I will need to find another job. However, DD1 will not yet be in school so can't see how I can find something which will pay for 2 lots of childcare. Even when DD1 starts school it will still mean paying for 9 hours per week childcare for her plus 27 hours for baby. I don't fancy putting her in afterschool club when she's in reception.
However I think I will have to find a job even if it all goes on childcare so we can re-mortgage - when our fixed rate runs out next May we may be in trouble trying to get a new mortgage on only one modest salary.
As well as working f/t my DH teaches 1 evening p/w and is hoping to increase to 2 evenings p/w, I think this could be difficult having him come home late trying to settle 2 kids on my own etc. but as least we'll have weekends together which some couples don't if one's working.
Like others I would like to keep my hand in workwise - I'm nervous about being out of the workplace for 15 months or more - but I'm not prepared to work for nothing (especially when dealing with being pregnant, tired etc). So I am just hoping that I will be able to find something suitable that pays enough when the time comes. Ideally during school hours so I can pick DD up from school, but as someone said school hours jobs are probably as rare as hens teeth!
I have thought we may have to move out of London to be able to afford to live - but then we'd both have to find work in a new town first.
There are no easy solutions!