Don't know either of those. At the moment I find the last movement of Prokofiev's Sonata in D really hard, but it doesn't crop up until FRSM so that'll be why! There was one study (no 74 in 76 Graded Studies for Flute) which I used to find really hard because there are seven flats in the key signature, but I perservered and got 28 for it in grade 8 so I dare say I'll be able to play the Prokofiev eventually!
Another piece I found really hard was the last movement of Bach's sonata in B minor. It used to be on grade eight but I dropped it and did the Mozart instead, and that Sonata doesn't crop up 'til FRSM again either. The thing with that was that the speed given on the music copy is incredibly fast, whereas when I heard a recording of it the speed was nothing like the metronome marking so that makes it more reasonable!
There's loads of other stuff, I'll probably post again after I go home and do some practice!
Helena