Sorry to crash but just thought I'd let you know that I think it's great that you're still going for the training even though it'll be hard - good on you!!
I don't know how it works but I'm pretty sure that you can get some help with child care e.g. paying by vouchers so you get it tax and NI free but your stp-mother would have to be registered. Also from about 3 children are entitled to free nursery places so although that won't help immediately it will do eventually!
See;
http://www.surestart.gov.uk/surestartservices/support/helpwithchildcarecosts/earlyeducationplaces/
for more details.
Sx