Resiting A-Levels or taking a gap year and doing an Scienc Access Course?

I currently hold offers for neuroscience at universities and i'm also a resit student so i'm technically third year at college/sixth form. I have not been in the best place and am thinking after this year, should I do foundation year or take a gap year and get myself together and then do an access to HE and get into neuroscience? Will universities allow this and accept me? Also, does anyone know about how an access course works?