Hiya.
I did this piece for my exam....Allegro Assai? I know which bits you mean...I can't find my book but its the mordents with Bb and Ab isn't it?
I play it differently from the cd but I usually do Bb AbBbAb I think, all in quick succession.
The key to this is not to rush. Try to develop your finger memory but playing it over and over agin VERY slowly, as the finger memory will defnitely help.
I'll reply again when I've found my book...