Go to the job centre (with an appointment is quicker) and they tell you all the stuff your entitled to, or ask your midwife about the Parents Guide to Money from the FSA
i got that when i was about 12 weeks and it tells you about all the options if at work or not before, during and after pregnancy
im not working for the first year (taking a gap year before uni) and we worked it out from the book i get around �120 a week (single parent) plus money from the dad through CSA
if you want to know now though the two main websites from the booklet are
www.parentsguidetomoney.fsa.gov.uk
www.moneymadeclear.fsa.gov.uk