Hi
It's 6 weeks full pay, followed by half pay + smp until the 6 month mark, then 3 months smp. You can then take a further 3 months maternity leave unpaid.
This is assuming that you have worked for the nhs for a certain amount of time (think you have had to be working for at least a week before your BFP). Also when you get half pay + smp this has to be less than your normal rate of pay, if your normal monthly wage is less than this you will get the lower amount.
Hope this has helped! x