Haven't worked at EY for a while, but it used to be:
Weeks 1-6 Statutory Maternity Pay (SMP) at 90% of relevant earnings
Weeks 7-22 Discretionary occupational maternity pay at 50% of notional salary before the commencement of maternity leave plus standard rate SMP at £112.75 per week (or 90% of notional salary, if lower)
Weeks 23-39 Standard rate SMP at £112.75 per week (or 90% of relevant earnings, if lower)
Weeks 40-52 No maternity pay