There are very very few places for postgraduate midwifery students at the minute and this is only going to decrease. Competition for these spaces is ridiculously hard and they only take the cream of the crop from nursing degrees across the country.
I really couldn't recommend that this is what you do because there is every likelihood that you would have to work as a nurse which isn't what you want to do for the rest of your life. If this is what you really want, contact some other colleges in the area and see if they would allow you to take biology. Although this isn't an ideal solution at the minute, if you work hard you will have a chance of getting straight onto the degree that you want to do.