I suggest you call the Citizen's Advice Bureau and book in for a Benefit Check.
My understanding, from a friend who works there (who has stressed that they cannot access the data kept in the office, so you should double check their info), is that while on maternity leave you are treated the same way as someone in employment, so you are entitled to child & working tax credits, housing benefit etc on that basis. This is paid up to a higher level than someone who is unemployed (in-work benefits always try to make work pay, so are more generous).
You will be treated as though you were working your usual hours before maternity leave when calculations are made. For a single mother, they need you to have been working 16 hrs week minimum, and a couple must be working at least 30 hrs between them to qualify.
When benefits are calculated, any child support payments you get are no longer factored in as relevant, on the grounds that too many absent parents simply aren't reliable enough to be able to do so. So that money is a bonus.
If you have a partner present and living with you, then obviously their income will be factored in when calculating benefit entitlement, if any.