You should be able to get child tax credit on that income if your daughter is living with you. You won't get much (£40-50 a month I think) but it will be better than nothing. Also child benefit could be transferred to you if you are parent with care.
You remind me of the story told by a Glaswegian lawyer about a father who after months of litigation was awarded sole residency because his ex-spouse was neglectful. On leaving the court he was panic stricken and grabbed the lawyer's arm and asked if that meant he actually had to care for the child.
PWC = parent with care
NRP = non resident parent
The Which? "Guide to Divorce and Splitting Up" is a good starting point for basic information.
Whilst everything gets sorted you could ask your lender for a mortgage payment holiday or if it's a repayment mortgage changing it to interest only. Basically to reach a capital settlement you add all his/her/ joint assets, including pensions, deduct any debts to reach a net total and the starting point for division is 50:50. Somewhere on the HMRC website it tells you about claiming CB, although perhaps in the interests of calming the situation you should consider waiting until you have more idea what will happen in the long term.
As far as your D is concerned you both automatically have Parental Responsibility and the majority of parents (about 90%) make their own arrangements. Courts have a principle of making no orders unless absolutely necessary as experience shows people tend to be more satisfied with agreed arrangements (and adhere to them better) than when they're imposed by court. There is a parenting plan downloadable from the Department of Constitutional Affairs website which will gives some idea of what arrangements need to be negotiated.
If you get the chance geldap , go to mediation. I cannot sing its praises enough. Even if you cant be in the same room with eachother they can still do wonders. My soon to be ex & me went in at loggerheads & came out both happy with our agreemant & good friends again aswell. DEFINATLY worth doing.
Have a look at the website entitledto.com it will let you know roughly what benefits you can claim. This will include child care cost if you have to use a childminder or day care facilities. PWC stands for Parent with care, dont look for to many problems at this stage wait till on comes up or you will get yourself it such a state, deal with the one that comes along, believe me there are answers to every question you will rise but dont get swamped by looking to far ahead.