Gah, I just typed up a big post and lost it...
If you can afford it, enroll in 2 subjects in the midwifery course and do those and do those really well. At out uni they advise doing the anatomy and physiology subjects, but you could also do a midwifery subject, and make yourself known to the lecturers so they remember you when you apply the following year. You would have to be able to work really hard though to get good marks, as they would use those subjects to help get you in.
Books wise, I would get Myles textbook for midwives, It is used in most courses I believe. It is incredibly similar to Mayes midwifery though. Also contact the uni you want to get into- maybe call their bookshop and ask what anatomy and physiology books are used at their uni for the subject that is in the midwifery course and work your way through that one. (0r ask a student on here if there is anyone from the uni you want to go to- there are heaps of girls on here and I am sure we would have most uni's covered.